一、概述

        lambda表达式是JDK8中的一个新特性，对某些匿名内部类进行简化，是函数式编程；

二、基本格式

        (参数列表)->{方法体代码}

三、Stream流

        是jdk8中的新特性，将数据以流的形式进行操作

三、常用方法解析

3.1、准备工作

@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode //用于后期的去重使用
@Data
public class People {
    private int id;
    private String name;
    private int age;
    private String home;
    private List<Friend> friendList;
}

@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode //用于后期的去重使用
@Data
public class Friend {
    private int id;
    private String name;
    private int age;
    private String home;
    private String category;//分类
}

 void contextLoads() {
        People people1=new People(1,"曹操",33,"魏国",null);
        People people2=new People(2,"孙权",15,"吴国",null);
        People people3=new People(3,"张飞",14,"蜀国",null);
        People people4=new People(3,"张飞",14,"蜀国",null);
        List<Friend>list1=new ArrayList<>();
        List<Friend>list2=new ArrayList<>();
        List<Friend>list3=new ArrayList<>();
        list1.add(new Friend(1,"刘备",88,"河北，石家庄","好朋友"));
        list1.add(new Friend(2,"赵云",99,"湖北，武汉","新朋友"));

        list2.add(new Friend(3,"周瑜",85,"辽宁，大连","老朋友"));
        list2.add(new Friend(3,"周瑜",85,"辽宁，大连","老朋友"));
        list2.add(new Friend(4,"诸葛亮",56,"内蒙古，包头","大朋友"));

        list3.add(new Friend(5,"郭嘉",56,"甘肃，兰州","骄傲的朋友"));
        list3.add(new Friend(6,"吕布",100,"陕西，西安","厉害的朋友"));
        list3.add(new Friend(7,"吕布",100,"陕西，西安","厉害的朋友"));

        people1.setFriendList(list1);
        people2.setFriendList(list2);
        people3.setFriendList(list3);
        people4.setFriendList(list3);

        List<People>peopleList=new ArrayList<>(Arrays.asList(people1,people2,people3,people4));
    }

 3.2、常用方法

//打印people年龄小于18的人的名字，且去重

peopleList.stream().distinct()
        .filter(new Predicate<People>() {
            @Override
            public boolean test(People people) {
                return people.getAge()<18;
            }
        }).forEach(new Consumer<People>() {
            @Override
            public void accept(People people) {
                System.out.println(people.getName());
            }
        });

-------------------------------Alt+Enter转为Lambda表达式-----------------------------
peopleList.stream()
        .distinct()
        .filter(people -> people.getAge()<18)
        .forEach(people -> System.out.println(people.getName()));