Java8之Steam API

package Java8;

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class TestLambda {

    public static void main(String[] args) {
        ArrayList list1 = new ArrayList();
        list1.add(1);
        list1.add(11);
        list1.add(12);
        list1.add(13);
        ArrayList list2 = new ArrayList();
        list2.add(1);
        list2.add(2);
        list2.add(3);
        Stream.of(list1).forEach(System.out::println);
        // 扁平化，合并两个列表，返回一个流
        Stream integerStream = Stream.of(list1, list2).flatMap(Collection::stream);
        System.out.println("integerStream: "+integerStream);
        // 将流变成一个集合
        List collect = Stream.of(list1, list2).flatMap(Collection::stream).collect(Collectors.toList());
        System.out.println("collect: "+collect);
        // 以流的方式去重
        List collect1 = Stream.of(list1, list2).flatMap(Collection::stream).distinct().collect(Collectors.toList());
        System.out.println("collect1: "+collect1);
        // 在流中过滤出符合条件的值
        List collect2 = Stream.of(list1, list2).flatMap(Collection::stream).distinct().filter(x -> x > 3).collect(Collectors.toList());
        System.out.println("collect2: "+collect2);
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

class People{
    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    public People(int age, String name){
        this.age = age;
        this.name = name;
    }

    int age;
    String name;
}
public class Test {
    public static void main(String[] args) {
        List list = new ArrayList();
        list.add(new People(1,"1"));
        list.add(new People(2,"2"));
        list.add(new People(3,"3"));
        Stream stream = list.stream();
//         在流中取出值
        Stream integerStream = stream.map(People::getAge);
        // 将值变为列表
        List collect = integerStream.collect(Collectors.toList());
//         过滤出年龄大于1的值
        Stream stream1 = list.stream();
        stream1.filter(p -> p.getAge() > 1).map(People::getAge).collect(Collectors.toList()).forEach(System.out::println);
        System.out.println("**************************");
        // reduce 取得流里的值，迭代操作。0->0+2->2+3->5
        Stream stream2 = list.stream();
        Integer reduce = stream2.filter(p -> p.getAge() > 1).map(People::getAge).reduce(0, Integer::sum);
        System.out.println(reduce);
    }
}