public class test7 { public static void main(String[] args) { ArrayList<UserEntity> list = new ArrayList<>(); list.add(new UserEntity("xialijun",12)); list.add(new UserEntity("xia",24)); list.add(new UserEntity("qwer",1234)); list.add(new UserEntity("qwet",1223)); list.add(new UserEntity("qwey",1235)); list.add(new UserEntity("qweye",1235)); //流: stream 串行流 单线程 // parallelStream() 并行流 多线程 效率高 // Set<UserEntity> collect = list.stream().collect(Collectors.toSet()); collect.forEach(x->{ System.out.println(x.toString()); }); System.out.println("========================================"); collect.forEach(System.out::println); Set<UserEntity> collect1 = list.parallelStream().collect(Collectors.toSet()); //key //UserEntity list 集合中的数据 第一种写法 : // Map<String, UserEntity> map = list.stream().collect(Collectors.toMap(new Function<UserEntity, String>() { // @Override // public String apply(UserEntity userEntity) { // return userEntity.getName(); // } // //value // }, new Function<UserEntity, UserEntity>() { // @Override // public UserEntity apply(UserEntity userEntity) { // return userEntity; // } // })); // map.forEach(new BiConsumer<String, UserEntity>() { // @Override // public void accept(String s, UserEntity userEntity) { // System.out.println(s + "====" + userEntity); // } // }); 第二种写法 Map<String, UserEntity> map = list.stream() //key----->UserEntity::getName, //value-----> userEntity -> userEntity .collect(Collectors.toMap(UserEntity::getName, userEntity -> userEntity)); map.forEach((s, userEntity) -> System.out.println(s + "====" + userEntity)); } }