Summary of 43 functions in Java 8, functional programming

Summary of 43 functions in Java 8

Based on the source code of Java8, this document is obtained by analyzing statistics and summarizing.

统计：
总共43个函数类
按函数的类别可分为5类
按参数个数可分为4类
按类型可以分为5类
继承关系：2个。大多数的函数类是没有继承关系的，仅仅靠类名称上的语义来保证关系的递进

1.5 types of functions

According to the class name, the keywords at the end are extracted and grouped to obtain 5 categories:

category	quantity	Summary	describe	method
Function	17	Function BiFunction type Function *3 type To type Function *6 To type Function *3 To type BiFunction *3	function. 1~2Parameters + 1return	R apply(T t); R apply(T t, U u); default compose(before); default andThen(after); static identity();
Consumer	8	Consumer BiConsumer type Consumer *3 Obj type Consumer *3	consumer. 1~2Parameters + 0return	void accept(T t); void accept(T t, U u); default andThen(after);
Operator	8	UnaryOperator BinaryOperator type UnaryOperator *3 type BinaryOperator *3	operate. 1~2Parameters + 1return	R apply(T t); R apply(T t, U u); int applyAsInt(int operand); static identity(); static minBy(comparator); static maxBy(comparator);
Predicate	5	Predicate BiPredicate DoublePredicate IntPredicate LongPredicate	Assertion, predicate. 1~2Parameters + 1return	boolean test(T t); default and(other); default negate(); default or(other); static isEqual(targetRef);
Supplier	5	Supplier BooleanSupplier DoubleSupplier IntSupplier LongSupplier	provider. 0Parameters + 1return	T get();

2. 4 parameter categories

All functions are divided into 1-parameter and 2-parameter functions.

category	quantity	Summary	describe	method
none	4	Among the 5 basic categories, except Operator Consumer, Function, Predicate, and Supplier	a parameter	xxx(T t);
Bi	6	BiConsumer BiFunction BiPredicate ToDoubleBiFunction ToIntBiFunction ToLongBiFunction	two parameters	xxx(T t, U u);
Unary	4	UnaryOperator DoubleUnaryOperator IntUnaryOperator LongUnaryOperator	Central operation	R apply(T t); static identity();
Binary	4	BinaryOperator DoubleBinaryOperator IntBinaryOperator LongBinaryOperator	Binary operations	R apply(T t, U u); static minBy(comparator); static maxBy(comparator);

2.1. The difference between “N parameters” and “N-element operation”:

N yuan	the difference	inheritance relationship
Unary	Differences from functions: The parameters and return value types of unary operations must be the same; the parameters and return types of functions can be different	UnaryOperator extends Function<T, T>
Binary	Differences from 2-parameter functions: The two operands and return value types of binary operations must be the same; while 2-parameter functions do not have this requirement	BinaryOperator extends BiFunction<T,T,T>

3. Type

Long	9
Int	9
Double	9
Obj	3	ObjDoubleConsumer ObjIntConsumer ObjLongConsumer
Boolean	1	BooleanSupplier

Help	4
ToInt	4
ToDouble	4

4、附录

原始的43个函数类，以及分解过程

编号	原始类名称	限定符1	限定符2	末尾
1	BiConsumer		Bi	Consumer
2	BiFunction		Bi	Function
3	BinaryOperator		Binary	Operator
4	BiPredicate		Bi	Predicate
5	BooleanSupplier		Boolean	Supplier
6	Consumer			Consumer
7	DoubleBinaryOperator	Double	Binary	Operator
8	DoubleConsumer		Double	Consumer
9	DoubleFunction		Double	Function
10	DoublePredicate		Double	Predicate
11	DoubleSupplier		Double	Supplier
12	DoubleToIntFunction	Double	ToInt	Function
13	DoubleToLongFunction	Double	ToLong	Function
14	DoubleUnaryOperator	Double	Unary	Operator
15	Function			Function
16	IntBinaryOperator	Int	Binary	Operator
17	IntConsumer		Int	Consumer
18	IntFunction		Int	Function
19	IntPredicate		Int	Predicate
20	IntSupplier		Int	Supplier
21	IntToDoubleFunction	Int	ToDouble	Function
22	IntToLongFunction	Int	ToLong	Function
23	IntUnaryOperator	Int	Unary	Operator
24	LongBinaryOperator	Long	Binary	Operator
25	LongConsumer		Long	Consumer
26	LongFunction		Long	Function
27	LongPredicate		Long	Predicate
28	LongSupplier		Long	Supplier
29	LongToDoubleFunction	Long	ToDouble	Function
30	LongToIntFunction	Long	ToInt	Function
31	LongUnaryOperator	Long	Unary	Operator
32	ObjDoubleConsumer	Obj	Double	Consumer
33	ObjIntConsumer	Obj	Int	Consumer
34	ObjLongConsumer	Obj	Long	Consumer
35	Predicate			Predicate
36	Supplier			Supplier
37	ToDoubleBiFunction	ToDouble	Bi	Function
38	ToDoubleFunction		ToDouble	Function
39	ToIntBiFunction	ToInt	Bi	Function
40	ToIntFunction		ToInt	Function
41	ToLongBiFunction	ToLong	Bi	Function
42	ToLongFunction		ToLong	Function
43	UnaryOperator		Unary	Operator

4.1 将拆分后的关键字分类

类型1	类型2	参数类型	函数类型
ToDouble	Double	Bi	Consumer
ToInt	Int	Binary	Function
ToLong	Long	Unary	Operator
	Obj		Predicate
	Boolean		Supplier