Java8新特性_四大内置核心函数式接口

四大内置核心函数式接口： 

package com.zs.boot.controller;

import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.function.Function;
import java.util.function.Supplier;

/*
 * Java8内置的四大核心函数式接口
 *
 * Consumer<T> : 消费型接口
 * 		void accept(T t);
 *
 * Supplier<T> : 供给型接口
 * 		T get();
 *
 * Function<T, R> : 函数型接口
 * 		R apply(T t);
 *
 * Predicate<T> : 断言型接口
 * 		boolean test(T t);
 *
 */
public class TestLambda4 {

    //Consumer<T> 消费型接口 :传进去一个参数，对参数进行一些操作，没有返回值
    @Test
    public void test1(){
        happy(10000, (m) -> System.out.println("我们吃饭每次消费：" + m + "元"));
    }

    public void happy(double money, Consumer<Double> con){
        con.accept(money);
    }

    //---------------------------------------------------------------

    //Supplier<T> 供给型接口 :没有参数，直接()
    @Test
    public void test2(){
        List<Integer> numList = getNumList(10, () -> (int)(Math.random() * 100));//100以内的随机整数

        for (Integer num : numList) {
            System.out.println(num);
        }
    }

    //需求：产生指定个数的整数，并放入集合中
    public List<Integer> getNumList(int num, Supplier<Integer> sup){
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < num; i++) {
            Integer n = sup.get();
            list.add(n);
        }
        return list;
    }

    //---------------------------------------------------------------

    //Function<T, R> 函数型接口：传进去一个参数，返回一个值
    @Test
    public void test3(){
        String newStr = strHandler("\t\t\t 哈哈哈威武   ", (str) -> str.trim());
        System.out.println(newStr);

        String subStr = strHandler("嘻嘻嘻嘻威武", (str) -> str.substring(2, 5));
        System.out.println(subStr);
    }

    //需求：用于处理字符串
    public String strHandler(String str, Function<String, String> fun){
        return fun.apply(str);
    }

    //---------------------------------------------------------------

    //Predicate<T> 断言型接口：
    @Test
    public void test4(){
        List<String> list = Arrays.asList("Hello", "atguigu", "Lambda", "www", "ok");
        List<String> strList = filterStr(list, (s) -> s.length() > 3);
        /*for (String str : strList) {
            System.out.println(str);
        }*/
        //用forEach遍历
        strList.forEach(System.out::println);
    }

    //需求：将满足条件的字符串，放入集合中
    public List<String> filterStr(List<String> list, Predicate<String> pre){
        List<String> strList = new ArrayList<>();
        for (String str : list) {
            if(pre.test(str)){
                strList.add(str);
            }
        }
        return strList;
    }

    //同理：我们可以把含有"京"字的字符串加入到list中去
    @Test
    public void test5(){
        List<String> list = Arrays.asList("Hello京", "atguigu", "Lambda", "www京", "ok");
        List<String> filterStrs1 = filterStr(list,s -> s.contains("京"));
        /*for (String str : strList) {
            System.out.println(str);
        }*/
        //用forEach遍历
        filterStrs1.forEach(System.out::println);
    }




}