| Return type | Name and parameters | 
|---|---|
| boolean | asBoolean()Coerce an Optionalinstance to abooleanvalue. | 
| Optional | collect(Closure transform)If a value is present in the Optional, returns transformed value
obtained using thetransformclosure 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 anOptionalDoubleconsisting 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 anOptionalIntconsisting 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 anOptionalLongconsisting of the result of applying the given function to the value or else empty. | 
| Optional | orOptional(Supplier supplier)Provides similar functionality to JDK9 oron JDK8. | 
| Optional | peek(Consumer action)If a value is present in the Optional, executes the specifiedactionwith the value as input and then returnsself. | 
| Stream | stream()If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream. | 
                                    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
                                
Coerce an Optional instance to a boolean value.
assert !Optional.empty().asBoolean() assert Optional.of(1234).asBoolean()
true if a value is present, false otherwiseIf 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()
                                    
                                    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)
                                    
                                    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() == []
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 == ''
                                    
                                    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
                                    
                                    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
                                    
                                    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
                                    
                                    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'
                                    
                                    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
                                    
                                    If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream.