Method 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

• <S, T> public Optional<T> collect(Closure<T> 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()
   

  Returns:

  an Optional containing the transformed value or empty if the input is empty or the transform returns null

  Since:

  3.0.0

• <T> public Optional<T> filter(Class<T> 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)
   

  Since:

  3.0.0

• <T, E> public Collection<T> flatten()

  Flatten an Optional. This yields a collection containing the Optional value if the Optional is present, or an empty collection otherwise.

  Example:

  
   assert Optional.of(1).flatten() == [1]
   assert Optional.empty().flatten() == []
   

  Returns:

  a flattened Optional

  Since:

  5.0.0

• <T> public T 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 == ''
   

  throws:

  IndexOutOfBoundsException if index is not 0 or -1

  Since:

  5.0.0

• <T> public OptionalDouble mapToDouble(ToDoubleFunction<? super T> 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
   

  Since:

  3.0.0

• <T> public OptionalInt mapToInt(ToIntFunction<? super T> 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
   

  Since:

  3.0.0

• <T> public OptionalLong mapToLong(ToLongFunction<? super T> 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
   

  Since:

  3.0.0

• <T> public Optional<T> orOptional(Supplier<Optional<? extends T>> 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'
   

  Since:

  3.0.6

• <T> public Optional<T> peek(Consumer<? super T> 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
   

  Since:

  5.0.0

• <T> public Stream<T> 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