Common Functional Interfaces

The table below gathers the mostly used functional interfaces within Java 8:

Functional Interface	Parameter Types	Return Type	Abstract Method Name	Description	Other Methods
Runnable	none	void	run	Runs an action without arguments or return value
Supplier	none	T	get	Supplies a value of type T
Consumer	T	void	accept	Consumes a value of type T	chain
BiConsumer	T, U	void	accept	Consumes values of types T and U	chain
Function	T	R	apply	A function with argument of type T	compose, andThen, identity
BiFunction	T, U	R	apply	A function with arguments of types T and U	andThen
UnaryOperator	T	T	apply	A unary operator on the type T	compose, andThen, identity
BinaryOperator	T, T	T	apply	A binary operator on the type T	andThen
Predicate	T	boolean	test	A Boolean-valued function	and, or, negate, isEqual
BiPredicate	T, U	boolean	test	A Boolean-valued function with two arguments	and, or, negate

Functional Interfaces for Primitive Types:

p, q is int, long, double;
P, Q is Int, Long, Double

Functional Interface	Parameter Types	Return Type	Abstract Method Name
BooleanSupplier	none	boolean	getAsBoolean
PSupplier	none	p	getAsP
PConsumer	p	void	accept
ObjPConsumer	T, p	void	accept
PFunction	p	T	apply
PToQFunction	p	q	applyAsQ
ToPFunction	T	p	applyAsP
ToPBiFunction	T, U	p	applyAsP
PUnaryOperator	p	p	applyAsP
PBinaryOperator	p, p	p	applyAsP
PPredicate	p	boolean	test