JAVA8源码学习-Function.class

package com.nikolas.java8;

import java.util.function.Function;

/**
 * @FunctionalInterface
 * 该注解的接口是函数式接口
 * 标注了该注解的接口都将能用在lambda表达式上。
 */
public class FunctionDemo {
    /***
     * R apply(T t);
     * 输入参数T
     * 返回结果R
     * R = f(t) = t + 1
     */
    public static Object apply(Integer argument){
        /**
         * 定义一个函数f(t) = t + 1;
         */
        Function<Integer,Integer> function = t->t+1;
        /**
         * 输入函数的入参argument 返回函数的值
         */
        return function.apply(argument);
    }


    /**
     * 定义:f1(X) = x+1
     * 定义:f2(x) = x*x
     * f3(X) = f1(X).compose(f2(X))
     * compose 将f2(x)的运算结果作为f1(x)的入参
     * f3(X) = f1(f2(x)) = (x*x)+1;
     * @param num 输入的参数
     */
    public static void compose(Long num){
        Function<Integer,Long> function1 = t ->Long.valueOf(t+1);
        Function<Long,Integer> function2 = t -> t.intValue()*t.intValue();
        Function<Long,Long> function3 = function1.compose(function2);
        System.out.println("测试3:"+function3.apply(num));
    }

    /**
     * 定义:f1(X) = x+1
     * 定义:f2(x) = x*x
     * f3(X) = f1(X).andThen(f2(X))
     * andThen 将f1(x)的运算结果作为f2(x)的入参
     * f3(X) = f2(f1(x)) = (X+1)*(x+1);
     * @param num 输入的参数
     */
    public static void andThen(Integer num){
        Function<Integer,Long> function1 = t ->Long.valueOf(t+1);
        Function<Long,Integer> function2 = t -> t.intValue()*t.intValue();
        Function<Integer,Integer> function3 = function1.andThen(function2);
        System.out.println("测试4:"+function3.apply(num));
    }

    public static void main(String[] args) {
        //测试1
        System.out.println("测试1:"+FunctionDemo.apply(8));

        //测试3
        FunctionDemo.compose(3L);

        //测试4
        FunctionDemo.andThen(3);
    }
}