Java8新特性:lambda表达式总结

() -> System.out.println( "Hello Lambda!" );

(x) -> System.out.println(x)

x -> System.out.println(x)

Comparator<Integer> com = (x, y) -> {

     System.out.println( "函数式接口" );

     return Integer测试数据pare(x, y);

};

Comparator<Integer> com = (x, y) -> Integer测试数据pare(x, y);

(Integer x, Integer y) -> Integer测试数据pare(x, y);

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);

package com.lyz.java8;

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;

import org.junit.Test;

/*

  * @author liuyazhuang

  * @version 1.0.0

  * @date 2018/8/19 15:02

  * @description 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 TestLambda {

     //Predicate<T> 断言型接口：

     @Test

     public void test4(){

         List<String> list = Arrays.asList( "Hello" , "world" , "Lambda" , "www" , "ok" );

         List<String> strList = filterStr(list, (s) -> s.length() > 3 );

         for (String str : strList) {

             System.out.println(str);

         }

     }

     //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;

     }

     //Function<T, R> 函数型接口：

     @Test

     public void test3(){

         String newStr = strHandler( "\t\t\t  我叫刘亚壮 " , (str) -> str.trim());

         System.out.println(newStr);

         String subStr = strHandler( "我叫刘亚壮" , (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);

     }

     //Supplier<T> 供给型接口 :

     @Test

     public void test2(){

         List<Integer> numList = getNumList( 10 , () -> ( int )(Math.random() * 100 ));

         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;

     }

     //Consumer<T> 消费型接口 :

     @Test

     public void test1(){

         happy( 10000 , (m) -> System.out.println( "每次消费：" + m + "元" ));

     }

     public void happy( double money, Consumer<Double> con){

         con.accept(money);

     }

}