java四大内置核心函数式接口

java四大内置核心函数式接口

Consumer : 消费型接口

​ void accept(T t)

Supplier : 供给型接口

​ T get()

Functrion<T,R>: 函数式接口

​ R apply(T t)

Predicate : 断言型接口

​ boolean test(T t)

代码示例：

package com.wxit.lambda;

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.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

/**
 * @Author wj
 **/
public class TestLambda4 {
    
    

    //Consumer<T>:消费型接口
    @Test
    public void test01(){
    
    
        eat(1000,m -> System.out.println("张三去和平饭店吃了一碗米饭，花了" + m + "块钱"));
    }

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

    //Supplier<T>:供给型接口
    @Test
    public void test02(){
    
    
        List<Integer> numList = getNumList(10, () -> (int) (Math.random()) * 100);

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

    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
    @Test
    public void test03(){
    
    
        String newStr = strHandler("\t\t\t\t轻轻地风儿轻轻地吹", (str) -> str.trim());
        System.out.println(newStr);
    }

    public String strHandler(String str, Function<String,String> fun){
    
    
        return fun.apply(str);
    }

    //Predicate<T> 断言型接口
    @Test
    public void test04(){
    
    
        List<String> list = Arrays.asList("qingqing","hellow","lambda","wu","hao");
        List<String> list1 = filterStr(list, (s) -> s.length() > 3);
        for (String s : list1) {
    
    
            System.out.println(s);
        }
    }

    //需求：将满足条件的字符串放入到集合中
    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;
    }
}