1、基本数据类型及String类型

• 1.JDK Set 去重

    public static void main(String[] args)
    {
        List<String> list = new ArrayList();
        list.add("123");list.add("123");
        Set<String> set = new HashSet<>(list);
        System.out.println(set);
    }

• 2. Java8 Stream

List<String> list = new ArrayList();
list.add("123");list.add("123");
List<String> ll = list.stream().distinct().collect(Collectors.toList());

2、List中对象去重

• 1. 重写对象中hashCode方法和equals方法 去重

@Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        User other = (User) obj;
        if (id == null) {
            if (other.id != null)
                return false;
        } else if (!id.equals(other.id))
            return false;
        return true;
    }

List<User> list = new ArrayList();
        User user1 = new User();
        user1.setId(1L); user1.setMobile("123456");
        list.add(user1);
        User user2 = new User();
        user2.setId(1L); user2.setMobile("12345678");
        list.add(user2);
// Set 去重
        Set<User> set = new HashSet<>(list);
        System.out.println(set);
//Java8 Stream
        List<User> userList = list.stream().distinct().collect(Collectors.toList());
        System.out.println(userList);

• Java8 Stream 去重

import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toCollection;
//根据id去重
        List<User> unique1 = list.stream().collect(
                collectingAndThen(
                        toCollection(() -> new TreeSet<>(comparing(User::getId))), ArrayList::new));
        System.out.println(unique1);
//根据id和mobile去重
        List<User> unique2 = list.stream().collect(
                collectingAndThen(
                        toCollection(() -> new TreeSet<>(comparing(o -> o.getId() + ";" + o.getMobile()))), ArrayList::new)
        );

        System.out.println(unique2);