| Return type | Name and parameters | 
|---|---|
| boolean | asBoolean()Coerce an Optionalinstance to abooleanvalue. | 
| Optional | collect(Closure transform)If the optional contains a value, returns an optional containing the transformed value obtained using the transformclosure
or otherwise an empty optional. | 
| Optional | filter(Class type)Tests given value against specified type and changes generics of result. | 
| 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)Provide similar functionality to JDK9 oron JDK8. | 
| 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, getAt, getMetaClass, getMetaPropertyValues, getProperties, grep, grep, hasProperty, identity, inject, inject, inspect, invokeMethod, is, isCase, 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, 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, otherwise falseIf the optional contains a value, returns an optional containing the transformed value obtained using the transform closure
or otherwise an empty optional.
assert Optional.of("foobar").collect{ it.size() }.get() == 6
assert !Optional.empty().collect{ it.size() }.isPresent()
                                    
                                    transform -  the closure used to transform the optional value if presentTests 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)
                                    
                                    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
                                    
                                    Provide similar functionality to JDK9 or on JDK8.
If a value is present in the Optional, returns a Stream with the value as its source or else an empty stream.