TreeSet

能自动对对象进行排序，但是一般需要在类中重写比较方法
比较器介绍

在类中实现Comparable接口，并重写compareTo方法

排序对象类

package typing.overridecompare;

public class Person  implements Comparable<Person>{
    private String name;
    private int age;
    
    Person() {
        
    }
    
    Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public String toString() {
        return "[name:" + name + ",age:" + age + "]";
    }
    
    public String getName() {
        return name;
    }
    
    public int getAge() {
        return age;
    }

    @Override
    public int compareTo(Person person) {
                // 先以年龄进行排序，再以姓名长度进行排序
        int num = this.getAge() - person.getAge();
        if (num==0) {
            num = this.getName().length() - person.getName().length();
        }
        
        return num;
        
    }
}

创建TreeSet对象并添加Person对象自动排序

package typing.overridecompare;

import java.util.Random;
import java.util.TreeSet;

public class OverrideCompareTo {
    private TreeSet<Integer> treeint;
    private TreeSet<Person> treeperson;
    
    public void treeInt() {
        treeint = new TreeSet<Integer>();
        Random r = new Random();
        for (int i = 0; i < 10; i ++)
            treeint.add(r.nextInt(100));
        System.out.println(treeint);
    }
    
    public void treePerson() {
        treeperson = new TreeSet<Person>();
        treeperson.add(new Person("ali",20));
        treeperson.add(new Person("aiya",16));
        treeperson.add(new Person("bob", 16));
        treeperson.add(new Person("boer", 21));
        treeperson.add(new Person("lobo",15));
        System.out.println(treeperson);
    }

}

测试类

            OverrideCompareTo compare = new OverrideCompareTo();
    compare.treePerson();//输出结果：[[name:lobo,age:15], [name:bob,age:16], [name:aiya,age:16], [name:ali,age:20], [name:boer,age:21]]

## 自定义比较器，在比较器中实现，需要实现Comparator接口并重写compare方法
自定义比较器类

package typing.overridecompare;

import java.util.Comparator;

public class CharCompare implements Comparator {

@Override
public int compare(Character c1, Character c2) {
    int num = c1 -c2;
    if (num == 0)
        num = 1;
    return num;// 以字符串的ascll顺序进行排序
    
}

}

测试类

TreeSet charset = new TreeSet (new CharCompare());// 在声明TreeSet时传入自定义比较器对象
Scanner input = new Scanner(System.in);
String line = input.nextLine();
char[] arr = line.toCharArray();
for (char ch:arr)
charset.add(ch);
System.out.println(charset);
// 输入abbcba,输出aabbbc
```