Optional (Groovy JDK enhancements)

Methods Summary

Methods
Return type	Name and parameters
`boolean`	`asBoolean()` Coerce an `Optional` instance to a `boolean` value.
`Optional`	`collect(Closure transform)` If a value is present in the `Optional`, returns transformed value obtained using the `transform` closure or no value as an optional.
`Optional`	`filter(Class type)` Tests given value against specified type and changes generics of result.
`Collection`	`flatten()` Flatten an Optional.
`Object`	`getAt(int index)` If a value is present in the `Optional`, returns the value or null.
`OptionalDouble`	`mapToDouble(ToDoubleFunction mapper)` If a value is present in the `Optional`, returns an `OptionalDouble` consisting of the result of applying the given function to the value or else empty.
`OptionalInt`	`mapToInt(ToIntFunction mapper)` If a value is present in the `Optional`, returns an `OptionalInt` consisting of the result of applying the given function to the value or else empty.
`OptionalLong`	`mapToLong(ToLongFunction mapper)` If a value is present in the `Optional`, returns an `OptionalLong` consisting of the result of applying the given function to the value or else empty.
`Optional`	`orOptional(Supplier supplier)` Provides similar functionality to JDK9 `or` on JDK8.
`Optional`	`peek(Consumer action)` If a value is present in the `Optional`, executes the specified `action` with the value as input and then returns `self`.
`Stream`	`stream()` If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream.

Methods inherited from class java.lang.Object

addShutdownHook, any, any, asBoolean, asType, collect, collect, collect, dump, each, eachMatch, eachMatch, eachWithIndex, every, every, find, find, findAll, findAll, findIndexOf, findIndexOf, findIndexValues, findIndexValues, findLastIndexOf, findLastIndexOf, findResult, findResult, findResult, findResult, getAt, getMetaClass, getMetaPropertyValues, getProperties, grep, grep, hasProperty, identity, inject, inject, inspect, invokeMethod, is, isCase, isNotCase, iterator, metaClass, print, print, printf, printf, println, println, println, putAt, respondsTo, respondsTo, setMetaClass, split, sprintf, sprintf, stream, tap, toString, use, use, use, with, with, withCloseable, withMethodClosure, withStream, withTraits

- Methods Detail
  - public boolean asBoolean()
    
    Coerce an Optional instance to a boolean value.
```
assert !Optional.empty().asBoolean()
assert Optional.of(1234).asBoolean()
```
    Returns:
    
    true if a value is present, false otherwise
    
    Since:
    
    2.5.0
  - public Optional collect(Closure transform)
    
    If a value is present in the Optional, returns transformed value obtained using the transform closure or no value as an optional.
```
assert Optional.of("foobar").collect{ it.size() }.get() == 6
assert !Optional.empty().collect{ it.size() }.isPresent()
```
    Parameters:
    
    Returns:
    
    an Optional containing the transformed value or empty if the input is empty or the transform returns null
    
    Since:
    
    3.0.0
  - public Optional filter(Class type)
    
    Tests given value against specified type and changes generics of result. This is equivalent to: self.filter(it -> it instanceof Type).map(it -> (Type) it)
```
assert !Optional.empty().filter(Number).isPresent()
assert !Optional.of('x').filter(Number).isPresent()
assert Optional.of(1234).filter(Number).isPresent()
assert Optional.of(1234).filter(Number).get().equals(1234)
```
    Parameters:
    
    Since:
    
    3.0.0
  - public Collection flatten()
    
    Flatten an Optional. This yields a collection containing the Optional value if the Optional is present, or an empty collect otherwise.
```
assert Optional.of(1).flatten() == [1]
assert Optional.empty().flatten() == []
```
    Returns:
    
    a flattened Optional
    
    Since:
    
    5.0.0
  - public Object getAt(int index)
    
    If a value is present in the Optional, returns the value or null.
```
def opt = Optional.empty()
assert opt[-1] == null
assert opt[0] == null
opt = Optional.of('')
assert opt[-1] == ''
assert opt[0] == ''

groovy.test.GroovyAssert.shouldFail(IndexOutOfBoundsException) { opt[1] }

// use via destructuring
opt = Optional.empty()
def (String s) = opt
assert s == null
opt = Optional.of('')
(s) = opt
assert s == ''
```
    Parameters:
    
    Since:
    
    5.0.0
  - public OptionalDouble mapToDouble(ToDoubleFunction mapper)
    
    If a value is present in the Optional, returns an OptionalDouble consisting of the result of applying the given function to the value or else empty.
```
assert !Optional.empty().mapToDouble(x -> Math.PI).isPresent()
assert  Optional.of('x').mapToDouble(x -> Math.PI).getAsDouble() == Math.PI
```
    Parameters:
    
    Since:
    
    3.0.0
  - public OptionalInt mapToInt(ToIntFunction mapper)
    
    If a value is present in the Optional, returns an OptionalInt consisting of the result of applying the given function to the value or else empty.
```
assert !Optional.empty().mapToInt(x -> 42).isPresent()
assert  Optional.of('x').mapToInt(x -> 42).getAsInt() == 42
```
    Parameters:
    
    Since:
    
    3.0.0
  - public OptionalLong mapToLong(ToLongFunction mapper)
    
    If a value is present in the Optional, returns an OptionalLong consisting of the result of applying the given function to the value or else empty.
```
assert !Optional.empty().mapToLong(x -> 42L).isPresent()
assert  Optional.of('x').mapToLong(x -> 42L).getAsLong() == 42L
```
    Parameters:
    
    Since:
    
    3.0.0
  - public Optional orOptional(Supplier supplier)
    
    Provides similar functionality to JDK9 or on JDK8.
```
def x = Optional.empty()
def y = Optional.of('y')
assert y.orOptional(() -> Optional.of('z')).get() == 'y'
assert x.orOptional(() -> Optional.of('z')).get() == 'z'
```
    Parameters:
    
    Since:
    
    3.0.6
  - public Optional peek(Consumer action)
    
    If a value is present in the Optional, executes the specified action with the value as input and then returns self.
```
boolean called = false
def opt = Optional.empty()
def out = opt.peek{ called = true }
assert out === opt
assert !called

opt = Optional.of('x')
out = opt.peek{ assert it == 'x'; called = true }
assert out === opt
assert called
```
    Parameters:
    
    Since:
    
    5.0.0
  - public Stream stream()
    
    If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream.
    
    Since:
    
    3.0.0

Class Optional

Methods Summary

Methods inherited from class java.lang.Object

Methods Detail

public boolean asBoolean()

public Optional collect(Closure transform)

public Optional filter(Class type)

public Collection flatten()

public Object getAt(int index)

public OptionalDouble mapToDouble(ToDoubleFunction mapper)

public OptionalInt mapToInt(ToIntFunction mapper)

public OptionalLong mapToLong(ToLongFunction mapper)

public Optional orOptional(Supplier supplier)

public Optional peek(Consumer action)

public Stream stream()