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.compare(x, y);
};

Comparator<Integer> com = (x, y) -> Integer.compare(x, y);

(Integer x, Integer y) -> Integer.compare(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);
	}
}