TreeSet

public class CollectionTest3 {

    public static void main(String[] args) {

        TreeSet set = new TreeSet();
        set.add(123);
        set.add(456);
        set.add(34);
        set.add(100);
        System.out.println(set);
    }
}

[34, 100, 123, 456]

import java.util.Objects;

/**
 * @author xianyu
 * @version 1.0
 * @date 2019/12/29 21:00
 */
public class Person implements Comparable{

    private String name;

    private Integer age;

    public Person() {
    }

    public Person(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return Objects.equals(name, person.name) &&
                Objects.equals(age, person.age);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    // 自然排序，安装姓名从大到小排列,再按照年龄从小到大排序
    @Override
    public int compareTo(Object o) {
        if(o instanceof Person){
            Person p = (Person)o; // 强转
            int compare = -this.name.compareTo(p.name);
            if(compare != 0){
                return compare;
            } else {
                return Integer.compare(this.age,p.age);
            }
        }else{
            throw new RuntimeException("输入的类型不匹配");
        }
    }
}

import java.util.Iterator;
import java.util.TreeSet;

/**
 * @author xianyu
 * @version 1.0
 * @date 2019/12/30 12:18
 * TreeSet
 */
public class CollectionTest3 {

    public static void main(String[] args) {

        TreeSet set = new TreeSet();
        set.add(new Person("Alice",23));
        set.add(new Person("Mike",20));
        set.add(new Person("Bob",18));
        set.add(new Person("Tom",22));
        set.add(new Person("Jerry",28));
        set.add(new Person("Bob",24));

        Iterator iterator = set.iterator();
        while(iterator.hasNext()){  // hasNext():判断是否还有下一个元素
            System.out.println(iterator.next());  // //next():①指针下移 ②将下移以后集合位置上的元素返回
        }

    }
}

Person{name='Tom', age=22}
Person{name='Mike', age=20}
Person{name='Jerry', age=28}
Person{name='Bob', age=18}
Person{name='Bob', age=24}
Person{name='Alice', age=23}

定制排序

import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;

/**
 * @author xianyu
 * @version 1.0
 * @date 2019/12/30 12:54
 * 定制排序
 */
public class CollectionTest4 {

    public static void main(String[] args) {
        Comparator com = new Comparator() {
            // 按照年龄从小到大排序
            @Override
            public int compare(Object o1, Object o2) {
                if(o1 instanceof Person && o2 instanceof Person){
                    Person p1 = (Person)o1;
                    Person p2 = (Person)o2;
                    return Integer.compare(p1.getAge(),p2.getAge());
                }else{
                    throw new RuntimeException("输入的数据类型不匹配");
                }
            }
        };

        TreeSet set = new TreeSet(com);

        set.add(new Person("Alice",23));
        set.add(new Person("Jack",18));
        set.add(new Person("Tom",22));
        set.add(new Person("Jerry",28));
        set.add(new Person("Bob",24));

        Iterator iterator = set.iterator();
        while(iterator.hasNext()){  // hasNext():判断是否还有下一个元素
            System.out.println(iterator.next());  // //next():①指针下移 ②将下移以后集合位置上的元素返回
        }

    }


}

Person{name='Jack', age=18}
Person{name='Tom', age=22}
Person{name='Alice', age=23}
Person{name='Bob', age=24}
Person{name='Jerry', age=28}