Iterable (Groovy JDK enhancements)

Methods Summary

Methods
Return type	Name and parameters
`boolean`	`any(Closure predicate)` Iterates over the contents of an iterable, and checks whether a predicate is valid for at least one element.
`Collection`	`asCollection()` Converts this Iterable to a Collection.
`List`	`asList()` Converts this Iterable to a List.
`Object`	`asType(Class clazz)` Converts the given iterable to another type.
`BufferedIterator`	`bufferedIterator()` Returns a `BufferedIterator` that allows examining the next element without consuming it.
`List`	`chop(int chopSizes)` Chops the Iterable into pieces, returning lists with sizes corresponding to the supplied chop sizes.
`List`	`collate(int size)` Collates this iterable into sub-lists of length `size`.
`List`	`collate(int size, boolean keepRemainder)` Collates this iterable into sub-lists of length `size`.
`List`	`collate(int size, int step)` Collates this iterable into sub-lists of length `size` stepping through the code `step` elements for each subList.
`List`	`collate(int size, int step, boolean keepRemainder)` Collates this iterable into sub-lists of length `size` stepping through the code `step` elements for each sub-list.
`List`	`collect()` Iterates through this collection transforming each entry into a new value using Closure.IDENTITY as a transformer, basically returning a list of items copied from the original collection.
`List`	`collect(Closure transform)` Iterates through this Iterable transforming each entry into a new value using the `transform` closure returning a list of transformed values.
`Collection`	`collect(Collection collector, Closure transform)` Iterates through this collection transforming each value into a new value using the `transform` closure and adding it to the supplied `collector`.
`Map`	`collectEntries()` A variant of collectEntries for Iterable objects using the identity closure as the transform.
`Map`	`collectEntries(Closure transform)` Iterates through this Iterable transforming each item using the `transform` closure and returning a map of the resulting transformed entries.
`Map`	`collectEntries(Map collector)` A variant of collectEntries for Iterables using the identity closure as the transform and a supplied map as the destination of transformed entries.
`Map`	`collectEntries(Map collector, Closure transform)` Iterates through this Iterable transforming each item using the closure as a transformer into a map entry, returning the supplied map with all of the transformed entries added to it.
`List`	`collectMany(Closure projection)` Projects each item from a source Iterable to a collection and concatenates (flattens) the resulting collections into a single list.
`Collection`	`collectMany(Collection collector, Closure projection)` Projects each item from a source collection to a result collection and concatenates (flattens) the resulting collections adding them into the `collector`.
`List`	`collectNested(Closure transform)` Recursively iterates through this Iterable transforming each non-Collection value into a new value using the closure as a transformer.
`Collection`	`collectNested(Collection collector, Closure transform)` Recursively iterates through this Iterable transforming each non-Collection value into a new value using the `transform` closure.
`List`	`combinations()` Adds GroovyCollections#combinations(Iterable) as a method on Iterables.
`List`	`combinations(Closure function)` Adds GroovyCollections#combinations(Iterable, Closure) as a method on collections.
`boolean`	`contains(Object item)` Returns `true` if this iterable contains the item.
`boolean`	`containsAll(Object[] items)` Returns `true` if this iterable contains all of the elements in the specified array.
`Number`	`count(Closure closure)` Counts the number of occurrences which satisfy the given closure from inside this Iterable.
`Number`	`count(Object value)` Counts the number of occurrences of the given value inside this Iterable.
`Map`	`countBy(Closure closure)` Sorts all collection members into groups determined by the supplied mapping closure and counts the group size.
`boolean`	`disjoint(Iterable right)` Returns `true` if the intersection of two iterables is empty.
`Collection`	`drop(int num)` Drops the given number of elements from the head of this Iterable.
`Collection`	`dropRight(int num)` Drops the given number of elements from the tail of this Iterable.
`Collection`	`dropWhile(Closure condition)` Returns a suffix of this Iterable where elements are dropped from the front while the given closure evaluates to true.
`Iterable`	`each(Closure closure)` Iterates through an Iterable, passing each item to the given closure.
`void`	`eachCombination(Closure function)` Applies a function on each combination of the input lists.
`Iterator`	`eachPermutation(Closure closure)` Iterates over all permutations of a collection, running a closure for each iteration.
`Iterable`	`eachWithIndex(Closure closure)` Iterates through an iterable type, passing each item and the item's index (a counter starting at zero) to the given closure.
`boolean`	`every(Closure predicate)` Used to determine if the given predicate closure is valid (i.e. returns `true` for all items in this iterable).
`int`	`findIndexOf(Closure condition)` Iterates over the elements of an Iterable and returns the index of the first item that satisfies the condition specified by the closure.
`int`	`findIndexOf(int startIndex, Closure condition)` Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index of the first item that satisfies the condition specified by the closure.
`List`	`findIndexValues(Closure condition)` Iterates over the elements of an Iterable and returns the index values of the items that match the condition specified in the closure.
`List`	`findIndexValues(Number startIndex, Closure condition)` Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index values of the items that match the condition specified in the closure.
`int`	`findLastIndexOf(Closure condition)` Iterates over the elements of an Iterable and returns the index of the last item that matches the condition specified in the closure.
`int`	`findLastIndexOf(int startIndex, Closure condition)` Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index of the last item that matches the condition specified in the closure.
`Object`	`findResult(Closure condition)` Iterates through the Iterable calling the given closure condition for each item but stopping once the first non-null result is found and returning that result.
`Object`	`findResult(Object defaultResult, Closure condition)` Iterates through the Iterable calling the given closure condition for each item but stopping once the first non-null result is found and returning that result.
`Collection`	`findResults(Closure filteringTransform)` Iterates through the Iterable transforming items using the supplied closure and collecting any non-null results.
`Object`	`first()` Returns the first item from the Iterable.
`Collection`	`flatten()` Flatten an Iterable.
`Collection`	`flatten(Closure flattenUsing)` Flatten an Iterable.
`Object`	`getAt(int idx)` Support the subscript operator for an Iterable.
`Map`	`groupBy(Closure closure)` Sorts all Iterable members into groups determined by the supplied mapping closure.
`Map`	`groupBy(Object closures)` Sorts all Iterable members into (sub)groups determined by the supplied mapping closures.
`Map`	`groupBy(List closures)` Sorts all Iterable members into (sub)groups determined by the supplied mapping closures.
`Object`	`head()` Returns the first item from the Iterable.
`Map`	`indexed()` Zips an Iterable with indices in (index, value) order.
`Map`	`indexed(int offset)` Zips an Iterable with indices in (index, value) order.
`Collection`	`init()` Returns the items from the Iterable excluding the last item.
`List`	`inits()` Calculates the init values of this Iterable: the first value will be this list of all items from the iterable and the final one will be an empty list, with the intervening values the results of successive applications of init on the items.
`Collection`	`intersect(Iterable right)` Create a Collection composed of the intersection of both iterables.
`Collection`	`intersect(Iterable right, Comparator comparator)` Create a Collection composed of the intersection of both iterables.
`boolean`	`isEmpty()` Check whether an `Iterable` has elements def items = [1] def iterable = { [ hasNext:{ !
`String`	`join(String separator)` Concatenates the `toString()` representation of each item in this Iterable, with the given String as a separator between each item.
`Object`	`last()` Returns the last item from the Iterable.
`Object`	`max()` Adds max() method to Iterable objects.
`Object`	`max(Closure closure)` Selects the item in the iterable which when passed as a parameter to the supplied closure returns the maximum value.
`Object`	`max(Comparator comparator)` Selects the maximum value found in the Iterable using the given comparator.
`Object`	`min()` Adds min() method to Collection objects.
`Object`	`min(Closure closure)` Selects the item in the iterable which when passed as a parameter to the supplied closure returns the minimum value.
`Object`	`min(Comparator comparator)` Selects the minimum value found in the Iterable using the given comparator.
`Collection`	`minus(Iterable removeMe)` Create a new Collection composed of the elements of the first Iterable minus every occurrence of elements of the given Iterable.
`Collection`	`minus(Object removeMe)` Create a new Collection composed of the elements of the first Iterable minus every occurrence of the given element to remove.
`Collection`	`multiply(Number factor)` Create a Collection composed of the elements of this Iterable, repeated a certain number of times.
`Set`	`permutations()` Finds all permutations of an iterable.
`List`	`permutations(Closure function)` Finds all permutations of an iterable, applies a function to each permutation and collects the result into a list.
`Collection`	`plus(Iterable right)` Create a Collection as a union of two iterables.
`Collection`	`plus(Object right)` Create a collection as a union of an Iterable and an Object.
`int`	`size()` Provide the standard Groovy `size()` method for `Iterable`.
`List`	`sort()` Sorts the Collection.
`List`	`sort(boolean mutate)` Sorts the Iterable.
`List`	`sort(boolean mutate, Closure closure)` Sorts this Iterable using the given Closure to determine the correct ordering.
`List`	`sort(boolean mutate, Comparator comparator)` Sorts the Iterable using the given Comparator.
`List`	`sort(Closure closure)` Sorts this Iterable using the given Closure to determine the correct ordering.
`Object`	`sum()` Sums the items in an Iterable.
`Object`	`sum(Closure closure)` Sums the result of apply a closure to each item of an Iterable.
`Object`	`sum(Object initialValue)` Sums the items in an Iterable, adding the result to some initial value.
`Object`	`sum(Object initialValue, Closure closure)` Sums the result of applying a closure to each item of an Iterable to some initial value.
`Collection`	`tail()` Returns the items from the Iterable excluding the first item.
`List`	`tails()` Calculates the tail values of this Iterable: the first value will be this list of all items from the iterable and the final one will be an empty list, with the intervening values the results of successive applications of tail on the items.
`Collection`	`take(int num)` Returns the first `num` elements from the head of this Iterable.
`Collection`	`takeRight(int num)` Returns the last `num` elements from the tail of this Iterable.
`Collection`	`takeWhile(Closure condition)` Returns a Collection containing the longest prefix of the elements from this Iterable where each element passed to the given closure evaluates to true.
`List`	`toList()` Convert an Iterable to a List.
`Set`	`toSet()` Convert an Iterable to a Set.
`List`	`toSorted()` Sorts the Iterable.
`List`	`toSorted(Closure closure)` Sorts this Iterable using the given Closure to determine the correct ordering.
`List`	`toSorted(Comparator comparator)` Sorts the Iterable using the given Comparator.
`SpreadMap`	`toSpreadMap()` Creates a spreadable map from this iterable.
`Collection`	`toUnique()` Returns a Collection containing the items from the Iterable but with duplicates removed using the natural ordering of the items to determine uniqueness.
`Collection`	`toUnique(Closure condition)` Returns a Collection containing the items from the Iterable but with duplicates removed.
`Collection`	`toUnique(Comparator comparator)` Returns a Collection containing the items from the Iterable but with duplicates removed.
`List`	`withIndex()` Zips an Iterable with indices in (value, index) order.
`List`	`withIndex(int offset)` Zips an Iterable with indices in (value, index) order.

- Methods Detail
  - public boolean any(Closure predicate)
    
    Iterates over the contents of an iterable, and checks whether a predicate is valid for at least one element.
```
assert [1, 2, 3].any { it == 2 }
assert ![1, 2, 3].any { it > 3 }
```
    Parameters:
    
    predicate - the closure predicate used for matching
    
    Returns:
    
    true if any iteration for the object matches the closure predicate
    
    Since:
    
    1.0
  - public Collection asCollection()
    
    Converts this Iterable to a Collection. Returns the original Iterable if it is already a Collection.
    Example usage:
```
assert new HashSet().asCollection() instanceof Collection
```
    Returns:
    
    a newly created List if this Iterable is not already a Collection
    
    Since:
    
    2.4.0
  - public List asList()
    
    Converts this Iterable to a List. Returns the original Iterable if it is already a List.
    Example usage:
```
assert new HashSet().asList() instanceof List
```
    Returns:
    
    a newly created List if this Iterable is not already a List
    
    Since:
    
    2.2.0
  - public Object asType(Class clazz)
    
    Converts the given iterable to another type.
    
    Parameters:
    
    clazz - the desired class
    
    Returns:
    
    the object resulting from this type conversion
    
    Since:
    
    2.4.12
    
    See Also:
    
    Collection#asType(Class)
  - public BufferedIterator bufferedIterator()
    
    Returns a BufferedIterator that allows examining the next element without consuming it.
```
assert new LinkedHashSet([1,2,3,4]).bufferedIterator().with { [head(), toList()] } == [1, [1,2,3,4]]
```
    Returns:
    
    a BufferedIterator for traversing self
    
    Since:
    
    2.5.0
  - public List chop(int chopSizes)
    
    Chops the Iterable into pieces, returning lists with sizes corresponding to the supplied chop sizes. If the Iterable isn't large enough, truncated (possibly empty) pieces are returned. Using a chop size of -1 will cause that piece to contain all remaining items from the Iterable.
    Example usage:
```
assert [1, 2, 3, 4].chop(1) == [[1]]
assert [1, 2, 3, 4].chop(1,-1) == [[1], [2, 3, 4]]
assert ('a'..'h').chop(2, 4) == [['a', 'b'], ['c', 'd', 'e', 'f']]
assert ['a', 'b', 'c', 'd', 'e'].chop(3) == [['a', 'b', 'c']]
assert ['a', 'b', 'c', 'd', 'e'].chop(1, 2, 3) == [['a'], ['b', 'c'], ['d', 'e']]
assert ['a', 'b', 'c', 'd', 'e'].chop(1, 2, 3, 3, 3) == [['a'], ['b', 'c'], ['d', 'e'], [], []]
```
    Parameters:
    
    chopSizes - the sizes for the returned pieces
    
    Returns:
    
    a list of lists chopping the original iterable into pieces determined by chopSizes
    
    Since:
    
    2.5.2
    
    See Also:
    
    Iterable#collate(int)
  - public List collate(int size)
    
    Collates this iterable into sub-lists of length size. Example:
```
def list = [ 1, 2, 3, 4, 5, 6, 7 ]
def coll = list.collate( 3 )
assert coll == [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7 ] ]
```
    Parameters:
    
    size - the length of each sub-list in the returned list
    
    Returns:
    
    a List containing the data collated into sub-lists
    
    Since:
    
    2.4.0
  - public List collate(int size, boolean keepRemainder)
    
    Collates this iterable into sub-lists of length size. Any remaining elements in the iterable after the subdivision will be dropped if keepRemainder is false. Example:
```
def list = [ 1, 2, 3, 4, 5, 6, 7 ]
def coll = list.collate( 3, false )
assert coll == [ [ 1, 2, 3 ], [ 4, 5, 6 ] ]
```
    Parameters:
    
    size - the length of each sub-list in the returned list
    
    keepRemainder - if true, any remaining elements are returned as sub-lists. Otherwise they are discarded
    
    Returns:
    
    a List containing the data collated into sub-lists
    
    Since:
    
    2.4.0
  - public List collate(int size, int step)
    
    Collates this iterable into sub-lists of length size stepping through the code step elements for each subList. Example:
```
def list = [ 1, 2, 3, 4 ]
def coll = list.collate( 3, 1 )
assert coll == [ [ 1, 2, 3 ], [ 2, 3, 4 ], [ 3, 4 ], [ 4 ] ]
```
    Parameters:
    
    size - the length of each sub-list in the returned list
    
    step - the number of elements to step through for each sub-list
    
    Returns:
    
    a List containing the data collated into sub-lists
    
    Since:
    
    2.4.0
  - public List collate(int size, int step, boolean keepRemainder)
    
    Collates this iterable into sub-lists of length size stepping through the code step elements for each sub-list. Any remaining elements in the iterable after the subdivision will be dropped if keepRemainder is false. Example:
```
def list = [ 1, 2, 3, 4 ]
assert list.collate( 2, 2, true  ) == [ [ 1, 2 ], [ 3, 4 ] ]
assert list.collate( 3, 1, true  ) == [ [ 1, 2, 3 ], [ 2, 3, 4 ], [ 3, 4 ], [ 4 ] ]
assert list.collate( 3, 1, false ) == [ [ 1, 2, 3 ], [ 2, 3, 4 ] ]
```
    Parameters:
    
    size - the length of each sub-list in the returned list
    
    step - the number of elements to step through for each sub-list
    
    keepRemainder - if true, any remaining elements are returned as sub-lists. Otherwise they are discarded
    
    Returns:
    
    a List containing the data collated into sub-lists
    
    Since:
    
    2.4.0
  - public List collect()
    
    Iterates through this collection transforming each entry into a new value using Closure.IDENTITY as a transformer, basically returning a list of items copied from the original collection.
```
assert [1,2,3] == [1,2,3].collect()
```
    Returns:
    
    a List of the transformed values
    
    Since:
    
    2.5.0
    
    See Also:
    
    Closure#IDENTITY
  - public List collect(Closure transform)
    
    Iterates through this Iterable transforming each entry into a new value using the transform closure returning a list of transformed values.
```
assert [2,4,6] == [1,2,3].collect { it * 2 }
```
    Parameters:
    
    transform - the closure used to transform each item of the collection
    
    Returns:
    
    a List of the transformed values
    
    Since:
    
    2.5.0
  - public Collection collect(Collection collector, Closure transform)
    
    Iterates through this collection transforming each value into a new value using the transform closure and adding it to the supplied collector.
```
assert [1,2,3] as HashSet == [2,4,5,6].collect(new HashSet()) { (int)(it / 2) }
```
    Parameters:
    
    collector - the Collection to which the transformed values are added
    
    transform - the closure used to transform each item
    
    Returns:
    
    the collector with all transformed values added to it
    
    Since:
    
    2.5.0
  - public Map collectEntries()
    
    A variant of collectEntries for Iterable objects using the identity closure as the transform. The source Iterable should contain a list of [key, value] tuples or Map.Entry objects.
```
def nums = [1, 10, 100, 1000]
def tuples = nums.collect{ [it, it.toString().size()] }
assert tuples == [[1, 1], [10, 2], [100, 3], [1000, 4]]
def map = tuples.collectEntries()
assert map == [1:1, 10:2, 100:3, 1000:4]
```
    Returns:
    
    a Map of the transformed entries
    
    Since:
    
    1.8.7
    
    See Also:
    
    Iterator#collectEntries()
  - public Map collectEntries(Closure transform)
    
    Iterates through this Iterable transforming each item using the transform closure and returning a map of the resulting transformed entries.
```
def letters = "abc"
// collect letters with index using list style
assert (0..2).collectEntries { index -> [index, letters[index]] } == [0:'a', 1:'b', 2:'c']
// collect letters with index using map style
assert (0..2).collectEntries { index -> [(index): letters[index]] } == [0:'a', 1:'b', 2:'c']
```
    Note: When using the list-style of result, the behavior is 'def (key, value) = listResultFromClosure'. While we strongly discourage using a list of size other than 2, Groovy's normal semantics apply in this case; throwing away elements after the second one and using null for the key or value for the case of a shortened list.
    
    Parameters:
    
    transform - the closure used for transforming, which has an item from self as the parameter and should return a Map.Entry, a Map or a two-element list containing the resulting key and value
    
    Returns:
    
    a Map of the transformed entries
    
    Since:
    
    1.8.7
    
    See Also:
    
    Iterator#collectEntries(Closure)
  - public Map collectEntries(Map collector)
    
    A variant of collectEntries for Iterables using the identity closure as the transform and a supplied map as the destination of transformed entries.
    
    Parameters:
    
    collector - the Map into which the transformed entries are put
    
    Returns:
    
    the collector with all transformed values added to it
    
    Since:
    
    1.8.7
    
    See Also:
    
    Iterator#collectEntries(Map)
  - public Map collectEntries(Map collector, Closure transform)
    
    Iterates through this Iterable transforming each item using the closure as a transformer into a map entry, returning the supplied map with all of the transformed entries added to it.
```
def letters = "abc"
// collect letters with index
assert (0..2).collectEntries( [:] ) { index -> [index, letters[index]] } == [0:'a', 1:'b', 2:'c']
assert (0..2).collectEntries( [4:'d'] ) { index ->
    [(index+1): letters[index]] } == [1:'a', 2:'b', 3:'c', 4:'d']
```
    Note: When using the list-style of result, the behavior is 'def (key, value) = listResultFromClosure'. While we strongly discourage using a list of size other than 2, Groovy's normal semantics apply in this case; throwing away elements after the second one and using null for the key or value for the case of a shortened list. If your collector Map doesn't support null keys or values, you might get a runtime error, e.g. NullPointerException or IllegalArgumentException.
    
    Parameters:
    
    collector - the Map into which the transformed entries are put
    
    transform - the closure used for transforming, which has an item from self as the parameter and should return a Map.Entry, a Map or a two-element list containing the resulting key and value
    
    Returns:
    
    the collector with all transformed values added to it
    
    Since:
    
    1.8.7
    
    See Also:
    
    Iterator#collectEntries(Map, Closure)
  - public List collectMany(Closure projection)
    
    Projects each item from a source Iterable to a collection and concatenates (flattens) the resulting collections into a single list.
```
def nums = 1..10
def squaresAndCubesOfEvens = nums.collectMany{ it % 2 ? [] : [it**2, it**3] }
assert squaresAndCubesOfEvens == [4, 8, 16, 64, 36, 216, 64, 512, 100, 1000]

def animals = ['CAT', 'DOG', 'ELEPHANT'] as Set
def smallAnimals = animals.collectMany{ it.size() > 3 ? [] : [it.toLowerCase()] }
assert smallAnimals == ['cat', 'dog']

def orig = nums as Set
def origPlusIncrements = orig.collectMany{ [it, it+1] }
assert origPlusIncrements.size() == orig.size() * 2
assert origPlusIncrements.unique().size() == orig.size() + 1
```
    Parameters:
    
    projection - a projecting Closure returning a collection of items
    
    Returns:
    
    a list created from the projected collections concatenated (flattened) together
    
    Since:
    
    2.2.0
    
    See Also:
    
    Collection#sum(groovy.lang.Closure)
  - public Collection collectMany(Collection collector, Closure projection)
    
    Projects each item from a source collection to a result collection and concatenates (flattens) the resulting collections adding them into the collector.
```
def animals = ['CAT', 'DOG', 'ELEPHANT'] as Set
def smallAnimals = animals.collectMany(['ant', 'bee']){ it.size() > 3 ? [] : [it.toLowerCase()] }
assert smallAnimals == ['ant', 'bee', 'cat', 'dog']

def nums = 1..5
def origPlusIncrements = nums.collectMany([] as Set){ [it, it+1] }
assert origPlusIncrements.size() == nums.size() + 1
```
    Parameters:
    
    collector - an initial collection to add the projected items to
    
    projection - a projecting Closure returning a collection of items
    
    Returns:
    
    the collector with the projected collections concatenated (flattened) into it
    
    Since:
    
    2.2.0
  - public List collectNested(Closure transform)
    
    Recursively iterates through this Iterable transforming each non-Collection value into a new value using the closure as a transformer. Returns a potentially nested list of transformed values.
```
assert [2,[4,6],[8],[]] == [1,[2,3],[4],[]].collectNested { it * 2 }
```
    Parameters:
    
    transform - the closure used to transform each item of the Iterable
    
    Returns:
    
    the resultant list
    
    Since:
    
    2.2.0
  - public Collection collectNested(Collection collector, Closure transform)
    
    Recursively iterates through this Iterable transforming each non-Collection value into a new value using the transform closure. Returns a potentially nested collection of transformed values.
```
def x = [1,[2,3],[4],[]].collectNested(new Vector()) { it * 2 }
assert x == [2,[4,6],[8],[]]
assert x instanceof Vector
```
    Parameters:
    
    collector - an initial Collection to which the transformed values are added
    
    transform - the closure used to transform each element of the Iterable
    
    Returns:
    
    the collector with all transformed values added to it
    
    Since:
    
    2.2.0
  - public List combinations()
    
    Adds GroovyCollections#combinations(Iterable) as a method on Iterables.
    Example usage:
```
assert [['a', 'b'],[1, 2, 3]].combinations() == [['a', 1], ['b', 1], ['a', 2], ['b', 2], ['a', 3], ['b', 3]]
```
    Returns:
    
    a List of the combinations found
    
    Since:
    
    2.2.0
    
    See Also:
    
    GroovyCollections#combinations(java.lang.Iterable)
  - public List combinations(Closure function)
    
    Adds GroovyCollections#combinations(Iterable, Closure) as a method on collections.
    Example usage:
```
assert [[2, 3],[4, 5, 6]].combinations {x,y -> x*y } == [8, 12, 10, 15, 12, 18]
```
    Parameters:
    
    function - a closure to be called on each combination
    
    Returns:
    
    a List of the results of applying the closure to each combinations found
    
    Since:
    
    2.2.0
    
    See Also:
    
    GroovyCollections#combinations(Iterable)
  - public boolean contains(Object item)
    
    Returns true if this iterable contains the item.
    
    Parameters:
    
    item - an Object to be checked for containment in this iterable
    
    Returns:
    
    true if this iterable contains the item
    
    Since:
    
    2.4.0
    
    See Also:
    
    Collection#contains(Object)
  - public boolean containsAll(Object[] items)
    
    Returns true if this iterable contains all of the elements in the specified array.
    
    Parameters:
    
    items - array to be checked for containment in this iterable
    
    Returns:
    
    true if this collection contains all of the elements in the specified array
    
    Since:
    
    2.4.0
    
    See Also:
    
    Collection#containsAll(Collection)
  - public Number count(Closure closure)
    
    Counts the number of occurrences which satisfy the given closure from inside this Iterable.
    Example usage:
```
assert [2,4,2,1,3,5,2,4,3].count{ it % 2 == 0 } == 5
```
    Parameters:
    
    closure - a closure condition
    
    Returns:
    
    the number of occurrences
    
    Since:
    
    2.2.0
  - public Number count(Object value)
    
    Counts the number of occurrences of the given value inside this Iterable. Comparison is done using Groovy's == operator (using compareTo(value) == 0 or equals(value) ).
    Example usage:
```
assert [2,4,2,1,3,5,2,4,3].count(4) == 2
```
    Parameters:
    
    value - the value being searched for
    
    Returns:
    
    the number of occurrences
    
    Since:
    
    2.2.0
  - public Map countBy(Closure closure)
    
    Sorts all collection members into groups determined by the supplied mapping closure and counts the group size. The closure should return the key that each item should be grouped by. The returned Map will have an entry for each distinct key returned from the closure, with each value being the frequency of items occurring for that group.
    Example usage:
```
assert [0:2, 1:3] == [1,2,3,4,5].countBy { it % 2 }
```
    Parameters:
    
    closure - a closure mapping items to the frequency keys
    
    Returns:
    
    a new Map grouped by keys with frequency counts
    
    Since:
    
    2.2.0
  - public boolean disjoint(Iterable right)
    
    Returns true if the intersection of two iterables is empty.
```
assert [1,2,3].disjoint([3,4,5]) == false
```
```
assert [1,2].disjoint([3,4]) == true
```
    Parameters:
    
    right - an Iterable
    
    Returns:
    
    boolean true if the intersection of two iterables is empty, false otherwise.
    
    Since:
    
    2.4.0
  - public Collection drop(int num)
    
    Drops the given number of elements from the head of this Iterable.
```
def strings = [ 'a', 'b', 'c' ]
assert strings.drop( 0 ) == [ 'a', 'b', 'c' ]
assert strings.drop( 2 ) == [ 'c' ]
assert strings.drop( 5 ) == []

class AbcIterable implements Iterable {
    Iterator iterator() { "abc".iterator() }
}
def abc = new AbcIterable()
assert abc.drop(0) == ['a', 'b', 'c']
assert abc.drop(1) == ['b', 'c']
assert abc.drop(3) == []
assert abc.drop(5) == []
```
    Parameters:
    
    num - the number of elements to drop from this Iterable
    
    Returns:
    
    a Collection consisting of all the elements of this Iterable minus the first num elements, or an empty list if it has less then num elements.
    
    Since:
    
    1.8.7
  - public Collection dropRight(int num)
    
    Drops the given number of elements from the tail of this Iterable.
```
def strings = [ 'a', 'b', 'c' ]
assert strings.dropRight( 0 ) == [ 'a', 'b', 'c' ]
assert strings.dropRight( 2 ) == [ 'a' ]
assert strings.dropRight( 5 ) == []

class AbcIterable implements Iterable {
    Iterator iterator() { "abc".iterator() }
}
def abc = new AbcIterable()
assert abc.dropRight(0) == ['a', 'b', 'c']
assert abc.dropRight(1) == ['a', 'b']
assert abc.dropRight(3) == []
assert abc.dropRight(5) == []
```
    Parameters:
    
    num - the number of elements to drop from this Iterable
    
    Returns:
    
    a Collection consisting of all the elements of this Iterable minus the last num elements, or an empty list if it has less then num elements.
    
    Since:
    
    2.4.0
  - public Collection dropWhile(Closure condition)
    
    Returns a suffix of this Iterable where elements are dropped from the front while the given closure evaluates to true.
```
class HorseIterable implements Iterable {
    Iterator iterator() { "horse".iterator() }
}
def horse = new HorseIterable()
assert horse.dropWhile{ it < 'r' } == ['r', 's', 'e']
assert horse.dropWhile{ it <= 'r' } == ['s', 'e']
```
    Parameters:
    
    condition - the closure that must evaluate to true to continue dropping elements
    
    Returns:
    
    a Collection containing the shortest suffix of the given Iterable such that the given closure condition evaluates to true for each element dropped from the front of the Iterable
    
    Since:
    
    1.8.7
  - public Iterable each(Closure closure)
    
    Iterates through an Iterable, passing each item to the given closure.
    
    Parameters:
    
    closure - the closure applied on each element found
    
    Returns:
    
    the self Iterable
  - public void eachCombination(Closure function)
    
    Applies a function on each combination of the input lists.
    Example usage:
```
[[2, 3],[4, 5, 6]].eachCombination { println "Found $it" }
```
    Parameters:
    
    function - a closure to be called on each combination
    
    Since:
    
    2.2.0
    
    See Also:
    
    GroovyCollections#combinations(Iterable)
  - public Iterator eachPermutation(Closure closure)
    
    Iterates over all permutations of a collection, running a closure for each iteration.
    Example usage:
```
def permutations = []
[1, 2, 3].eachPermutation{ permutations << it }
assert permutations == [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]
```
    Parameters:
    
    closure - the closure to call for each permutation
    
    Returns:
    
    the permutations from the list
    
    Since:
    
    1.7.0
  - public Iterable eachWithIndex(Closure closure)
    
    Iterates through an iterable type, passing each item and the item's index (a counter starting at zero) to the given closure.
    
    Parameters:
    
    closure - a Closure to operate on each item
    
    Returns:
    
    the self Iterable
    
    Since:
    
    2.3.0
  - public boolean every(Closure predicate)
    
    Used to determine if the given predicate closure is valid (i.e. returns true for all items in this iterable). A simple example for a list:
```
def list = [3,4,5]
def greaterThanTwo = list.every { it > 2 }
```
    Parameters:
    
    predicate - the closure predicate used for matching
    
    Returns:
    
    true if every iteration of the object matches the closure predicate
    
    Since:
    
    2.3.0
  - public int findIndexOf(Closure condition)
    
    Iterates over the elements of an Iterable and returns the index of the first item that satisfies the condition specified by the closure.
    
    Parameters:
    
    condition - the matching condition
    
    Returns:
    
    an integer that is the index of the first matched object or -1 if no match was found
    
    Since:
    
    2.5.0
  - public int findIndexOf(int startIndex, Closure condition)
    
    Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index of the first item that satisfies the condition specified by the closure.
    
    Parameters:
    
    startIndex - start matching from this index
    
    condition - the matching condition
    
    Returns:
    
    an integer that is the index of the first matched object or -1 if no match was found
    
    Since:
    
    2.5.0
  - public List findIndexValues(Closure condition)
    
    Iterates over the elements of an Iterable and returns the index values of the items that match the condition specified in the closure.
    
    Parameters:
    
    condition - the matching condition
    
    Returns:
    
    a list of numbers corresponding to the index values of all matched objects
    
    Since:
    
    2.5.0
  - public List findIndexValues(Number startIndex, Closure condition)
    
    Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index values of the items that match the condition specified in the closure.
    
    Parameters:
    
    startIndex - start matching from this index
    
    condition - the matching condition
    
    Returns:
    
    a list of numbers corresponding to the index values of all matched objects
    
    Since:
    
    2.5.0
  - public int findLastIndexOf(Closure condition)
    
    Iterates over the elements of an Iterable and returns the index of the last item that matches the condition specified in the closure.
    
    Parameters:
    
    condition - the matching condition
    
    Returns:
    
    an integer that is the index of the last matched object or -1 if no match was found
    
    Since:
    
    2.5.0
  - public int findLastIndexOf(int startIndex, Closure condition)
    
    Iterates over the elements of an Iterable, starting from a specified startIndex, and returns the index of the last item that matches the condition specified in the closure.
    
    Parameters:
    
    startIndex - start matching from this index
    
    condition - the matching condition
    
    Returns:
    
    an integer that is the index of the last matched object or -1 if no match was found
    
    Since:
    
    2.5.0
  - public Object findResult(Closure condition)
    
    Iterates through the Iterable calling the given closure condition for each item but stopping once the first non-null result is found and returning that result. If all results are null, null is returned.
    
    Parameters:
    
    condition - a closure that returns a non-null value to indicate that processing should stop and the value should be returned
    
    Returns:
    
    the first non-null result from calling the closure, or null
    
    Since:
    
    2.5.0
  - public Object findResult(Object defaultResult, Closure condition)
    
    Iterates through the Iterable calling the given closure condition for each item but stopping once the first non-null result is found and returning that result. If all are null, the defaultResult is returned.
    Examples:
```
def list = [1,2,3]
assert "Found 2" == list.findResult("default") { it > 1 ? "Found $it" : null }
assert "default" == list.findResult("default") { it > 3 ? "Found $it" : null }
```
    Parameters:
    
    defaultResult - an Object that should be returned if all closure results are null
    
    condition - a closure that returns a non-null value to indicate that processing should stop and the value should be returned
    
    Returns:
    
    the first non-null result from calling the closure, or the defaultValue
    
    Since:
    
    2.5.0
  - public Collection findResults(Closure filteringTransform)
    
    Iterates through the Iterable transforming items using the supplied closure and collecting any non-null results.
    Example:
```
def list = [1,2,3]
def result = list.findResults { it > 1 ? "Found $it" : null }
assert result == ["Found 2", "Found 3"]
```
    Parameters:
    
    filteringTransform - a Closure that should return either a non-null transformed value or null for items which should be discarded
    
    Returns:
    
    the list of non-null transformed values
    
    Since:
    
    2.2.0
  - public Object first()
    
    Returns the first item from the Iterable.
```
def set = [3, 4, 2] as LinkedHashSet
assert set.first() == 3
// check original is unaltered
assert set == [3, 4, 2] as Set
```
    The first element returned by the Iterable's iterator is returned. If the Iterable doesn't guarantee a defined order it may appear like a random element is returned.
    
    Returns:
    
    the first item from the Iterable
    
    Since:
    
    1.8.7
  - public Collection flatten()
    
    Flatten an Iterable. This Iterable and any nested arrays or collections have their contents (recursively) added to the new collection.
```
assert [1,2,3,4,5] == [1,[2,3],[[4]],[],5].flatten()
```
    Returns:
    
    a flattened Collection
    
    Since:
    
    1.6.0
  - public Collection flatten(Closure flattenUsing)
    
    Flatten an Iterable. This Iterable and any nested arrays or collections have their contents (recursively) added to the new collection. For any non-Array, non-Collection object which represents some sort of collective type, the supplied closure should yield the contained items; otherwise, the closure should just return any element which corresponds to a leaf.
    
    Parameters:
    
    flattenUsing - a closure to determine how to flatten non-Array, non-Collection elements
    
    Returns:
    
    a flattened Collection
    
    Since:
    
    1.6.0
  - public Object getAt(int idx)
    
    Support the subscript operator for an Iterable. Typical usage:
```
// custom Iterable example:
class MyIterable implements Iterable {
  Iterator iterator() { [1, 2, 3].iterator() }
}
def myIterable = new MyIterable()
assert myIterable[1] == 2

// Set example:
def set = [1,2,3] as LinkedHashSet
assert set[1] == 2
```
    Parameters:
    
    idx - an index value (-self.size() <= idx < self.size()) but using -ve index values will be inefficient
    
    Returns:
    
    the value at the given index (after normalisation) or null if no corresponding value was found
    
    Since:
    
    2.1.0
  - public Map groupBy(Closure closure)
    
    Sorts all Iterable members into groups determined by the supplied mapping closure. The closure should return the key that this item should be grouped by. The returned LinkedHashMap will have an entry for each distinct key returned from the closure, with each value being a list of items for that group.
    Example usage:
```
assert [0:[2,4,6], 1:[1,3,5]] == [1,2,3,4,5,6].groupBy { it % 2 }
```
    Parameters:
    
    closure - a closure mapping entries on keys
    
    Returns:
    
    a new Map grouped by keys
    
    Since:
    
    2.2.0
  - public Map groupBy(Object closures)
    
    Sorts all Iterable members into (sub)groups determined by the supplied mapping closures. Each closure should return the key that this item should be grouped by. The returned LinkedHashMap will have an entry for each distinct 'key path' returned from the closures, with each value being a list of items for that 'group path'. Example usage:
```
def result = [1,2,3,4,5,6].groupBy({ it % 2 }, { it < 4 })
assert result == [1:[(true):[1, 3], (false):[5]], 0:[(true):[2], (false):[4, 6]]]
```
    Another example:
```
def sql = groovy.sql.Sql.newInstance(/* ... */)
def data = sql.rows("SELECT * FROM a_table").groupBy({ it.column1 }, { it.column2 }, { it.column3 })
if (data.val1.val2.val3) {
    // there exists a record where:
    //   a_table.column1 == val1
    //   a_table.column2 == val2, and
    //   a_table.column3 == val3
} else {
    // there is no such record
}
```
    If an empty array of closures is supplied the IDENTITY Closure will be used.
    
    Parameters:
    
    closures - an array of closures, each mapping entries on keys
    
    Returns:
    
    a new Map grouped by keys on each criterion
    
    Since:
    
    2.2.0
    
    See Also:
    
    Closure#IDENTITY
  - public Map groupBy(List closures)
    
    Sorts all Iterable members into (sub)groups determined by the supplied mapping closures. Each closure should return the key that this item should be grouped by. The returned LinkedHashMap will have an entry for each distinct 'key path' returned from the closures, with each value being a list of items for that 'group path'. Example usage:
```
def result = [1,2,3,4,5,6].groupBy([{ it % 2 }, { it < 4 }])
assert result == [1:[(true):[1, 3], (false):[5]], 0:[(true):[2], (false):[4, 6]]]
```
    Another example:
```
def sql = groovy.sql.Sql.newInstance(/* ... */)
def data = sql.rows("SELECT * FROM a_table").groupBy([{ it.column1 }, { it.column2 }, { it.column3 }])
if (data.val1.val2.val3) {
    // there exists a record where:
    //   a_table.column1 == val1
    //   a_table.column2 == val2, and
    //   a_table.column3 == val3
} else {
    // there is no such record
}
```
    If an empty list of closures is supplied the IDENTITY Closure will be used.
    
    Parameters:
    
    closures - a list of closures, each mapping entries on keys
    
    Returns:
    
    a new Map grouped by keys on each criterion
    
    Since:
    
    2.2.0
    
    See Also:
    
    Closure#IDENTITY
  - public Object head()
    
    Returns the first item from the Iterable.
```
def set = [3, 4, 2] as LinkedHashSet
assert set.head() == 3
// check original is unaltered
assert set == [3, 4, 2] as Set
```
    The first element returned by the Iterable's iterator is returned. If the Iterable doesn't guarantee a defined order it may appear like a random element is returned.
    
    Returns:
    
    the first item from the Iterable
    
    Since:
    
    2.4.0
  - public Map indexed()
    
    Zips an Iterable with indices in (index, value) order.
    Example usage:
```
assert [0: "a", 1: "b"] == ["a", "b"].indexed()
assert ["0: a", "1: b"] == ["a", "b"].indexed().collect { idx, str -> "$idx: $str" }
```
    Returns:
    
    a zipped map with indices
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#withIndex()
  - public Map indexed(int offset)
    
    Zips an Iterable with indices in (index, value) order.
    Example usage:
```
assert [5: "a", 6: "b"] == ["a", "b"].indexed(5)
assert ["1: a", "2: b"] == ["a", "b"].indexed(1).collect { idx, str -> "$idx: $str" }
```
    Parameters:
    
    offset - an index to start from
    
    Returns:
    
    a Map (since the keys/indices are unique) containing the elements from the iterable zipped with indices
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#withIndex(int)
  - public Collection init()
    
    Returns the items from the Iterable excluding the last item. Leaves the original Iterable unchanged.
```
def list = [3, 4, 2]
assert list.init() == [3, 4]
assert list == [3, 4, 2]
```
    Returns:
    
    a Collection without its last element
    
    Since:
    
    2.4.0
  - public List inits()
    
    Calculates the init values of this Iterable: the first value will be this list of all items from the iterable and the final one will be an empty list, with the intervening values the results of successive applications of init on the items.
```
assert [1, 2, 3, 4].inits() == [[1, 2, 3, 4], [1, 2, 3], [1, 2], [1], []]
```
    Returns:
    
    a List of the init values from the given Iterable
    
    Since:
    
    2.5.0
  - public Collection intersect(Iterable right)
    
    Create a Collection composed of the intersection of both iterables. Any elements that exist in both iterables are added to the resultant collection. For iterables of custom objects; the objects should implement java.lang.Comparable
```
assert [4,5] == [1,2,3,4,5].intersect([4,5,6,7,8])
```
    By default, Groovy uses a NumberAwareComparator when determining if an element exists in both collections.
    
    Parameters:
    
    right - an Iterable
    
    Returns:
    
    a Collection as an intersection of both iterables
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#intersect(Iterable, Comparator)
  - public Collection intersect(Iterable right, Comparator comparator)
    
    Create a Collection composed of the intersection of both iterables. Any elements that exist in both iterables are added to the resultant collection. For iterables of custom objects; the objects should implement java.lang.Comparable
    
    Parameters:
    
    right - an Iterable
    
    comparator - a Comparator
    
    Returns:
    
    a Collection as an intersection of both iterables
    
    Since:
    
    2.5.0
  - public boolean isEmpty()
    
    Check whether an Iterable has elements
```
def items = [1]
def iterable = { [ hasNext:{ !items.isEmpty() }, next:{ items.pop() } ] as Iterator } as Iterable
assert !iterable.isEmpty()
iterable.iterator().next()
assert iterable.isEmpty()
```
    Returns:
    
    true if the iterable has no elements, false otherwise
    
    Since:
    
    2.5.0
  - public String join(String separator)
    
    Concatenates the toString() representation of each item in this Iterable, with the given String as a separator between each item.
```
assert "1, 2, 3" == [1,2,3].join(", ")
```
    Parameters:
    
    separator - a String separator
    
    Returns:
    
    the joined String
    
    Since:
    
    1.0
  - public Object last()
    
    Returns the last item from the Iterable.
```
def set = [3, 4, 2] as LinkedHashSet
assert set.last() == 2
// check original unaltered
assert set == [3, 4, 2] as Set
```
    The last element returned by the Iterable's iterator is returned. If the Iterable doesn't guarantee a defined order it may appear like a random element is returned.
    
    Returns:
    
    the last item from the Iterable
    
    Since:
    
    1.8.7
  - public Object max()
    
    Adds max() method to Iterable objects.
```
assert 5 == [2,3,1,5,4].max()
```
    Returns:
    
    the maximum value
    
    Since:
    
    2.2.0
    
    See Also:
    
    GroovyCollections#max(java.lang.Iterable)
  - public Object max(Closure closure)
    
    Selects the item in the iterable which when passed as a parameter to the supplied closure returns the maximum value. A null return value represents the least possible return value, so any item for which the supplied closure returns null, won't be selected (unless all items return null). If more than one item has the maximum value, an arbitrary choice is made between the items having the maximum value.
    If the closure has two parameters it is used like a traditional Comparator. I.e. it should compare its two parameters for order, returning a negative integer, zero, or a positive integer when the first parameter is less than, equal to, or greater than the second respectively. Otherwise, the Closure is assumed to take a single parameter and return a Comparable (typically an Integer) which is then used for further comparison.
```
assert "hello" == ["hello","hi","hey"].max { it.length() }
```
```
assert "hello" == ["hello","hi","hey"].max { a, b -> a.length() <=> b.length() }
```
```
def pets = ['dog', 'elephant', 'anaconda']
def longestName = pets.max{ it.size() } // one of 'elephant' or 'anaconda'
assert longestName.size() == 8
```
    Parameters:
    
    closure - a 1 or 2 arg Closure used to determine the correct ordering
    
    Returns:
    
    an item from the Iterable having the maximum value returned by calling the supplied closure with that item as parameter or null for an empty Iterable
    
    Since:
    
    2.2.0
  - public Object max(Comparator comparator)
    
    Selects the maximum value found in the Iterable using the given comparator.
```
assert "hello" == ["hello","hi","hey"].max( { a, b -> a.length() <=> b.length() } as Comparator )
```
    Parameters:
    
    comparator - a Comparator
    
    Returns:
    
    the maximum value or null for an empty Iterable
    
    Since:
    
    2.2.0
  - public Object min()
    
    Adds min() method to Collection objects.
```
assert 2 == [4,2,5].min()
```
    Returns:
    
    the minimum value
    
    Since:
    
    1.0
    
    See Also:
    
    GroovyCollections#min(java.util.Collection)
  - public Object min(Closure closure)
    
    Selects the item in the iterable which when passed as a parameter to the supplied closure returns the minimum value. A null return value represents the least possible return value. If more than one item has the minimum value, an arbitrary choice is made between the items having the minimum value.
    If the closure has two parameters it is used like a traditional Comparator. I.e. it should compare its two parameters for order, returning a negative integer, zero, or a positive integer when the first parameter is less than, equal to, or greater than the second respectively. Otherwise, the Closure is assumed to take a single parameter and return a Comparable (typically an Integer) which is then used for further comparison.
```
assert "hi" == ["hello","hi","hey"].min { it.length() }
```
```
def lastDigit = { a, b -> a % 10 <=> b % 10 }
assert [19, 55, 91].min(lastDigit) == 91
```
```
def pets = ['dog', 'cat', 'anaconda']
def shortestName = pets.min{ it.size() } // one of 'dog' or 'cat'
assert shortestName.size() == 3
```
    Parameters:
    
    closure - a 1 or 2 arg Closure used to determine the correct ordering
    
    Returns:
    
    an item from the Iterable having the minimum value returned by calling the supplied closure with that item as parameter or null for an empty Iterable
    
    Since:
    
    1.0
  - public Object min(Comparator comparator)
    
    Selects the minimum value found in the Iterable using the given comparator.
```
assert "hi" == ["hello","hi","hey"].min( { a, b -> a.length() <=> b.length() } as Comparator )
```
    Parameters:
    
    comparator - a Comparator
    
    Returns:
    
    the minimum value or null for an empty Iterable
    
    Since:
    
    2.2.0
  - public Collection minus(Iterable removeMe)
    
    Create a new Collection composed of the elements of the first Iterable minus every occurrence of elements of the given Iterable.
```
assert [1, "a", true, true, false, 5.3] - [true, 5.3] == [1, "a", false]
```
    Parameters:
    
    removeMe - an Iterable of elements to remove
    
    Returns:
    
    a new Collection with the given elements removed
    
    Since:
    
    2.4.0
  - public Collection minus(Object removeMe)
    
    Create a new Collection composed of the elements of the first Iterable minus every occurrence of the given element to remove.
```
assert ["a", 5, 5, true] - 5 == ["a", true]
```
    Parameters:
    
    removeMe - an element to remove from the Iterable
    
    Returns:
    
    the resulting Collection with the given element removed
    
    Since:
    
    2.4.0
  - public Collection multiply(Number factor)
    
    Create a Collection composed of the elements of this Iterable, repeated a certain number of times. Note that for non-primitive elements, multiple references to the same instance will be added.
```
assert [1,2,3,1,2,3] == [1,2,3] * 2
```
    Note: if the Iterable happens to not support duplicates, e.g. a Set, then the method will effectively return a Collection with a single copy of the Iterable's items.
    
    Parameters:
    
    factor - the number of times to append
    
    Returns:
    
    the multiplied Collection
    
    Since:
    
    2.4.0
  - public Set permutations()
    
    Finds all permutations of an iterable.
    Example usage:
```
def result = [1, 2, 3].permutations()
assert result == [[3, 2, 1], [3, 1, 2], [1, 3, 2], [2, 3, 1], [2, 1, 3], [1, 2, 3]] as Set
```
    Returns:
    
    the permutations from the list
    
    Since:
    
    1.7.0
  - public List permutations(Closure function)
    
    Finds all permutations of an iterable, applies a function to each permutation and collects the result into a list.
    Example usage:
```
Set result = [1, 2, 3].permutations { it.collect { v -> 2*v }}
assert result == [[6, 4, 2], [6, 2, 4], [2, 6, 4], [4, 6, 2], [4, 2, 6], [2, 4, 6]] as Set
```
    Parameters:
    
    function - the function to apply on each permutation
    
    Returns:
    
    the list of results of the application of the function on each permutation
    
    Since:
    
    2.2.0
  - public Collection plus(Iterable right)
    
    Create a Collection as a union of two iterables. If the left iterable is a Set, then the returned collection will be a Set otherwise a List. This operation will always create a new object for the result, while the operands remain unchanged.
```
assert [1,2,3,4] == [1,2] + [3,4]
```
    Parameters:
    
    right - the right Iterable
    
    Returns:
    
    the merged Collection
    
    Since:
    
    2.4.0
  - public Collection plus(Object right)
    
    Create a collection as a union of an Iterable and an Object. If the iterable is a Set, then the returned collection will be a Set otherwise a List. This operation will always create a new object for the result, while the operands remain unchanged.
```
assert [1,2,3] == [1,2] + 3
```
    Parameters:
    
    right - an object to add/append
    
    Returns:
    
    the resulting Collection
    
    Since:
    
    2.4.0
  - public int size()
    
    Provide the standard Groovy size() method for Iterable.
```
def items = [1, 2, 3]
def iterable = { [ hasNext:{ !items.isEmpty() }, next:{ items.pop() } ] as Iterator } as Iterable
assert iterable.size() == 3
```
    Returns:
    
    the length of the Iterable
    
    Since:
    
    2.3.8
  - public List sort()
    
    Sorts the Collection. Assumes that the collection items are comparable and uses their natural ordering to determine the resulting order. If the Collection is a List, it is sorted in place and returned. Otherwise, the elements are first placed into a new list which is then sorted and returned - leaving the original Collection unchanged.
```
assert [1,2,3] == [3,1,2].sort()
```
    Returns:
    
    the sorted Iterable as a List
    
    Since:
    
    2.2.0
    
    See Also:
    
    Collection#sort(boolean)
  - public List sort(boolean mutate)
    
    Sorts the Iterable. Assumes that the Iterable items are comparable and uses their natural ordering to determine the resulting order. If the Iterable is a List and mutate is true, it is sorted in place and returned. Otherwise, the elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
```
assert [1,2,3] == [3,1,2].sort()
```
```
def orig = [1, 3, 2]
def sorted = orig.sort(false)
assert orig == [1, 3, 2]
assert sorted == [1, 2, 3]
```
    Parameters:
    
    mutate - false will always cause a new list to be created, true will mutate lists in place
    
    Returns:
    
    the sorted iterable as a List
    
    Since:
    
    2.2.0
  - public List sort(boolean mutate, Closure closure)
    
    Sorts this Iterable using the given Closure to determine the correct ordering. If the Iterable is a List and mutate is true, it is sorted in place and returned. Otherwise, the elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
    If the closure has two parameters it is used like a traditional Comparator. I.e. it should compare its two parameters for order, returning a negative integer, zero, or a positive integer when the first parameter is less than, equal to, or greater than the second respectively. Otherwise, the Closure is assumed to take a single parameter and return a Comparable (typically an Integer) which is then used for further comparison.
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { it.length() }
```
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { a, b -> a.length() <=> b.length() }
```
```
def orig = ["hello","hi","Hey"]
def sorted = orig.sort(false) { it.toUpperCase() }
assert orig == ["hello","hi","Hey"]
assert sorted == ["hello","Hey","hi"]
```
    Parameters:
    
    mutate - false will always cause a new list to be created, true will mutate lists in place
    
    closure - a 1 or 2 arg Closure used to determine the correct ordering
    
    Returns:
    
    a newly created sorted List
    
    Since:
    
    2.2.0
  - public List sort(boolean mutate, Comparator comparator)
    
    Sorts the Iterable using the given Comparator. If the Iterable is a List and mutate is true, it is sorted in place and returned. Otherwise, the elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort(false, { a, b -> a.length() <=> b.length() } as Comparator )
```
```
def orig = ["hello","hi","Hey"]
def sorted = orig.sort(false, String.CASE_INSENSITIVE_ORDER)
assert orig == ["hello","hi","Hey"]
assert sorted == ["hello","Hey","hi"]
```
    Parameters:
    
    mutate - false will always cause a new list to be created, true will mutate lists in place
    
    comparator - a Comparator used for the comparison
    
    Returns:
    
    a sorted List
    
    Since:
    
    2.2.0
  - public List sort(Closure closure)
    
    Sorts this Iterable using the given Closure to determine the correct ordering. If the Iterable is a List, it is sorted in place and returned. Otherwise, the elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
    If the Closure has two parameters it is used like a traditional Comparator. I.e. it should compare its two parameters for order, returning a negative integer, zero, or a positive integer when the first parameter is less than, equal to, or greater than the second respectively. Otherwise, the Closure is assumed to take a single parameter and return a Comparable (typically an Integer) which is then used for further comparison.
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { it.length() }
```
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { a, b -> a.length() <=> b.length() }
```
    Parameters:
    
    closure - a 1 or 2 arg Closure used to determine the correct ordering
    
    Returns:
    
    a newly created sorted List
    
    Since:
    
    2.2.0
    
    See Also:
    
    Collection#sort(boolean, Closure)
  - public Object sum()
    
    Sums the items in an Iterable. This is equivalent to invoking the "plus" method on all items in the Iterable.
```
assert 1+2+3+4 == [1,2,3,4].sum()
```
    Returns:
    
    The sum of all of the items
    
    Since:
    
    2.2.0
  - public Object sum(Closure closure)
    
    Sums the result of apply a closure to each item of an Iterable. coll.sum(closure) is equivalent to: coll.collect(closure).sum().
```
assert 4+6+10+12 == [2,3,5,6].sum { it * 2 }
```
    Parameters:
    
    closure - a single parameter closure that returns a numeric value.
    
    Returns:
    
    The sum of the values returned by applying the closure to each item of the Iterable.
    
    Since:
    
    2.2.0
  - public Object sum(Object initialValue)
    
    Sums the items in an Iterable, adding the result to some initial value.
```
assert 5+1+2+3+4 == [1,2,3,4].sum(5)
```
    Parameters:
    
    initialValue - the items in the collection will be summed to this initial value
    
    Returns:
    
    The sum of all of the items.
    
    Since:
    
    2.2.0
  - public Object sum(Object initialValue, Closure closure)
    
    Sums the result of applying a closure to each item of an Iterable to some initial value. coll.sum(initVal, closure) is equivalent to: coll.collect(closure).sum(initVal).
```
assert 50+4+6+10+12 == [2,3,5,6].sum(50) { it * 2 }
```
    Parameters:
    
    closure - a single parameter closure that returns a numeric value.
    
    initialValue - the closure results will be summed to this initial value
    
    Returns:
    
    The sum of the values returned by applying the closure to each item of the collection.
    
    Since:
    
    1.5.0
  - public Collection tail()
    
    Returns the items from the Iterable excluding the first item.
```
def list = [3, 4, 2]
assert list.tail() == [4, 2]
assert list == [3, 4, 2]
```
    Returns:
    
    a collection without its first element
    
    Since:
    
    2.4.0
  - public List tails()
    
    Calculates the tail values of this Iterable: the first value will be this list of all items from the iterable and the final one will be an empty list, with the intervening values the results of successive applications of tail on the items.
```
assert [1, 2, 3, 4].tails() == [[1, 2, 3, 4], [2, 3, 4], [3, 4], [4], []]
```
    Returns:
    
    a List of the tail values from the given Iterable
    
    Since:
    
    2.5.0
  - public Collection take(int num)
    
    Returns the first num elements from the head of this Iterable.
```
def strings = [ 'a', 'b', 'c' ]
assert strings.take( 0 ) == []
assert strings.take( 2 ) == [ 'a', 'b' ]
assert strings.take( 5 ) == [ 'a', 'b', 'c' ]

class AbcIterable implements Iterable {
    Iterator iterator() { "abc".iterator() }
}
def abc = new AbcIterable()
assert abc.take(0) == []
assert abc.take(1) == ['a']
assert abc.take(3) == ['a', 'b', 'c']
assert abc.take(5) == ['a', 'b', 'c']
```
    Parameters:
    
    num - the number of elements to take from this Iterable
    
    Returns:
    
    a Collection consisting of the first num elements from this Iterable, or else all the elements from the Iterable if it has less then num elements.
    
    Since:
    
    1.8.7
  - public Collection takeRight(int num)
    
    Returns the last num elements from the tail of this Iterable.
```
def strings = [ 'a', 'b', 'c' ]
assert strings.takeRight( 0 ) == []
assert strings.takeRight( 2 ) == [ 'b', 'c' ]
assert strings.takeRight( 5 ) == [ 'a', 'b', 'c' ]

class AbcIterable implements Iterable {
    Iterator iterator() { "abc".iterator() }
}
def abc = new AbcIterable()
assert abc.takeRight(0) == []
assert abc.takeRight(1) == ['c']
assert abc.takeRight(3) == ['a', 'b', 'c']
assert abc.takeRight(5) == ['a', 'b', 'c']
```
    Parameters:
    
    num - the number of elements to take from this Iterable
    
    Returns:
    
    a Collection consisting of the last num elements from this Iterable, or else all the elements from the Iterable if it has less then num elements.
    
    Since:
    
    2.4.0
  - public Collection takeWhile(Closure condition)
    
    Returns a Collection containing the longest prefix of the elements from this Iterable where each element passed to the given closure evaluates to true.
```
class AbcIterable implements Iterable {
    Iterator iterator() { "abc".iterator() }
}
def abc = new AbcIterable()
assert abc.takeWhile{ it < 'b' } == ['a']
assert abc.takeWhile{ it <= 'b' } == ['a', 'b']
```
    Parameters:
    
    condition - the closure that must evaluate to true to continue taking elements
    
    Returns:
    
    a Collection containing a prefix of the elements from the given Iterable where each element passed to the given closure evaluates to true
    
    Since:
    
    1.8.7
  - public List toList()
    
    Convert an Iterable to a List. The Iterable's iterator will become exhausted of elements after making this conversion.
    Example usage:
```
def x = [1,2,3] as HashSet
assert x.class == HashSet
assert x.toList() instanceof List
```
    Returns:
    
    a List
    
    Since:
    
    1.8.7
  - public Set toSet()
    
    Convert an Iterable to a Set. Always returns a new Set even if the Iterable is already a Set.
    Example usage:
```
def result = [1, 2, 2, 2, 3].toSet()
assert result instanceof Set
assert result == [1, 2, 3] as Set
```
    Returns:
    
    a Set
    
    Since:
    
    2.4.0
  - public List toSorted()
    
    Sorts the Iterable. Assumes that the Iterable elements are comparable and uses a NumberAwareComparator to determine the resulting order. NumberAwareComparator has special treatment for numbers but otherwise uses the natural ordering of the Iterable elements. The elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
```
def orig = [1, 3, 2]
def sorted = orig.toSorted()
assert orig == [1, 3, 2]
assert sorted == [1, 2, 3]
```
    Returns:
    
    the sorted iterable as a List
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#toSorted(Comparator)
  - public List toSorted(Closure closure)
    
    Sorts this Iterable using the given Closure to determine the correct ordering. The elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
    If the Closure has two parameters it is used like a traditional Comparator. I.e. it should compare its two parameters for order, returning a negative integer, zero, or a positive integer when the first parameter is less than, equal to, or greater than the second respectively. Otherwise, the Closure is assumed to take a single parameter and return a Comparable (typically an Integer) which is then used for further comparison.
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { it.length() }
```
```
assert ["hi","hey","hello"] == ["hello","hi","hey"].sort { a, b -> a.length() <=> b.length() }
```
    Parameters:
    
    closure - a 1 or 2 arg Closure used to determine the correct ordering
    
    Returns:
    
    a newly created sorted List
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#toSorted(Comparator)
  - public List toSorted(Comparator comparator)
    
    Sorts the Iterable using the given Comparator. The elements are first placed into a new list which is then sorted and returned - leaving the original Iterable unchanged.
```
def orig = ["hello","hi","Hey"]
def sorted = orig.toSorted(String.CASE_INSENSITIVE_ORDER)
assert orig == ["hello","hi","Hey"]
assert sorted == ["hello","Hey","hi"]
```
    Parameters:
    
    comparator - a Comparator used for the comparison
    
    Returns:
    
    a sorted List
    
    Since:
    
    2.4.0
  - public SpreadMap toSpreadMap()
    
    Creates a spreadable map from this iterable.
    
    Returns:
    
    a newly created SpreadMap
    
    Since:
    
    2.4.0
    
    See Also:
    
    SpreadMap#SpreadMap(java.util.List)
    
    Map#toSpreadMap()
  - public Collection toUnique()
    
    Returns a Collection containing the items from the Iterable but with duplicates removed using the natural ordering of the items to determine uniqueness.
```
String[] letters = ['c', 'a', 't', 's', 'a', 't', 'h', 'a', 't']
String[] expected = ['c', 'a', 't', 's', 'h']
assert letters.toUnique() == expected
```
    Returns:
    
    the Collection of non-duplicate items
    
    Since:
    
    2.4.0
  - public Collection toUnique(Closure condition)
    
    Returns a Collection containing the items from the Iterable but with duplicates removed. The items in the Iterable are compared by the given Closure condition. For each duplicate, the first member which is returned from the Iterable is retained, but all other ones are removed.
    If the closure takes a single parameter, each element from the Iterable will be passed to the closure. The closure should return a value used for comparison (either using Comparable#compareTo(java.lang.Object) or Object#equals(java.lang.Object)). If the closure takes two parameters, two items from the Iterable will be passed as arguments, and the closure should return an int value (with 0 indicating the items are not unique).
```
class Person {
    def fname, lname
    String toString() {
        return fname + " " + lname
    }
}

Person a = new Person(fname:"John", lname:"Taylor")
Person b = new Person(fname:"Clark", lname:"Taylor")
Person c = new Person(fname:"Tom", lname:"Cruz")
Person d = new Person(fname:"Clark", lname:"Taylor")

def list = [a, b, c, d]
def list2 = list.toUnique{ p1, p2 -> p1.lname != p2.lname ? p1.lname <=> p2.lname : p1.fname <=> p2.fname }
assert( list2 == [a, b, c] && list == [a, b, c, d] )
def list3 = list.toUnique{ it.toString() }
assert( list3 == [a, b, c] && list == [a, b, c, d] )
```
    Parameters:
    
    condition - a Closure used to determine unique items
    
    Returns:
    
    a new Collection
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#toUnique(Comparator)
  - public Collection toUnique(Comparator comparator)
    
    Returns a Collection containing the items from the Iterable but with duplicates removed. The items in the Iterable are compared by the given Comparator. For each duplicate, the first member which is returned from the Iterable is retained, but all other ones are removed.
```
class Person {
    def fname, lname
    String toString() {
        return fname + " " + lname
    }
}

class PersonComparator implements Comparator {
    int compare(Object o1, Object o2) {
        Person p1 = (Person) o1
        Person p2 = (Person) o2
        if (p1.lname != p2.lname)
            return p1.lname.compareTo(p2.lname)
        else
            return p1.fname.compareTo(p2.fname)
    }

    boolean equals(Object obj) {
        return this.equals(obj)
    }
}

Person a = new Person(fname:"John", lname:"Taylor")
Person b = new Person(fname:"Clark", lname:"Taylor")
Person c = new Person(fname:"Tom", lname:"Cruz")
Person d = new Person(fname:"Clark", lname:"Taylor")

def list = [a, b, c, d]
List list2 = list.toUnique(new PersonComparator())
assert list2 == [a, b, c] && list == [a, b, c, d]
```
    Parameters:
    
    comparator - a Comparator used to determine unique (equal) items If null, the Comparable natural ordering of the elements will be used.
    
    Returns:
    
    the Collection of non-duplicate items
    
    Since:
    
    2.4.0
  - public List withIndex()
    
    Zips an Iterable with indices in (value, index) order.
    Example usage:
```
assert [["a", 0], ["b", 1]] == ["a", "b"].withIndex()
assert ["0: a", "1: b"] == ["a", "b"].withIndex().collect { str, idx -> "$idx: $str" }
```
    Returns:
    
    a zipped list with indices
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#indexed()
  - public List withIndex(int offset)
    
    Zips an Iterable with indices in (value, index) order.
    Example usage:
```
assert [["a", 5], ["b", 6]] == ["a", "b"].withIndex(5)
assert ["1: a", "2: b"] == ["a", "b"].withIndex(1).collect { str, idx -> "$idx: $str" }
```
    Parameters:
    
    offset - an index to start from
    
    Returns:
    
    a zipped list with indices
    
    Since:
    
    2.4.0
    
    See Also:
    
    Iterable#indexed(int)

Interface Iterable

Methods Summary

Methods Detail

public boolean any(Closure predicate)

public Collection asCollection()

public List asList()

public Object asType(Class clazz)

public BufferedIterator bufferedIterator()

public List chop(int chopSizes)

public List collate(int size)

public List collate(int size, boolean keepRemainder)

public List collate(int size, int step)

public List collate(int size, int step, boolean keepRemainder)

public List collect()

public List collect(Closure transform)

public Collection collect(Collection collector, Closure transform)

public Map collectEntries()

public Map collectEntries(Closure transform)

public Map collectEntries(Map collector)

public Map collectEntries(Map collector, Closure transform)

public List collectMany(Closure projection)

public Collection collectMany(Collection collector, Closure projection)

public List collectNested(Closure transform)

public Collection collectNested(Collection collector, Closure transform)

public List combinations()

public List combinations(Closure function)

public boolean contains(Object item)

public boolean containsAll(Object[] items)

public Number count(Closure closure)

public Number count(Object value)

public Map countBy(Closure closure)

public boolean disjoint(Iterable right)

public Collection drop(int num)

public Collection dropRight(int num)

public Collection dropWhile(Closure condition)

public Iterable each(Closure closure)

public void eachCombination(Closure function)

public Iterator eachPermutation(Closure closure)

public Iterable eachWithIndex(Closure closure)

public boolean every(Closure predicate)

public int findIndexOf(Closure condition)

public int findIndexOf(int startIndex, Closure condition)

public List findIndexValues(Closure condition)

public List findIndexValues(Number startIndex, Closure condition)

public int findLastIndexOf(Closure condition)

public int findLastIndexOf(int startIndex, Closure condition)

public Object findResult(Closure condition)

public Object findResult(Object defaultResult, Closure condition)

public Collection findResults(Closure filteringTransform)

public Object first()

public Collection flatten()

public Collection flatten(Closure flattenUsing)

public Object getAt(int idx)

public Map groupBy(Closure closure)

public Map groupBy(Object closures)

public Map groupBy(List closures)

public Object head()

public Map indexed()

public Map indexed(int offset)

public Collection init()

public List inits()

public Collection intersect(Iterable right)

public Collection intersect(Iterable right, Comparator comparator)

public boolean isEmpty()

public String join(String separator)

public Object last()

public Object max()

public Object max(Closure closure)

public Object max(Comparator comparator)

public Object min()

public Object min(Closure closure)

public Object min(Comparator comparator)

public Collection minus(Iterable removeMe)

public Collection minus(Object removeMe)

public Collection multiply(Number factor)

public Set permutations()

public List permutations(Closure function)

public Collection plus(Iterable right)

public Collection plus(Object right)

public int size()