TreeMap保存自定义对象,比较的Comparable和Comparator两种方式

package com.jd.text;

import java.util.Set;
import java.util.TreeMap;

/*
* TreeMap保存自定义对象,比较的Comparable和Comparator两种方式
* 1.通过实现Comparable接口，重写compareTo()方法。
*/
public class Demo07 {

public static void main(String[] args) {
TreeMap map=new TreeMap<>();
map.put(new User("张三01", 12),11);
map.put(new User("张三01", 10),11);
map.put(new User("张三02", 13),11);
map.put(new User("张三01", 12),11);
//通过重写hashCode()和equals( obj)方法防止重复的值存入
Set set = map.keySet();
for ( key : set) {
value = map.get(key);
System.out.println(key + ":" + value);
}
}
}

package com.jd.text;
/*
 * 通过实现Comparable接口，重写compareTo()方法。
 */
public class User implements Comparable{

    private String name;
    private int age;
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
    public User(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public User() {
        super();
    }
    
    @Override
    public int hashCode() {
        final int prime=31;
        int result=1;
        result=prime*result+age;
        result=prime*result+((name==null)?0:name.hashCode());
        return result;
    }
    @Override
    public boolean equals(  obj) {
        if(this==obj)
            return true;
        if(obj==null)
            return false;
        if(getClass()!=obj.getClass())
            return false;
        User user=(User) obj;
        if(age!=user.age)
            return false;
        if(name==null){
            if(user.name!=null)
                return false;
        }else if(!name.equals(user.name))
            return false;
        return true;
    }
    @Override
    public int compareTo(  o) {
        if(o instanceof User){
            User user=(User) o;
            int sum=name.compareTo(user.name);
            if(sum==0)
                return age-user.age;
            return sum;
        }
        throw new ClassCastException("不是User类型");
    }
    
}

User [name=张三01, age=10]:11
User [name=张三01, age=12]:11
User [name=张三02, age=13]:11

package com.jd.text;
/*
 * TreeMap保存自定义对象,比较的Comparable和Comparator两种方式
 * 2.自己构造比较器实现Comparator接口，重写compare(  o1,   o2)方法
 */

import java.util.Comparator;
import java.util.Set;
import java.util.TreeMap;

public class Demo08 {

    public static void main(String[] args) {
        TreeMap map=new TreeMap(new MyCompare());
        map.put(new User2("张三01", 12),11);
        map.put(new User2("张三01", 10),11);
        map.put(new User2("张三02", 13),11);
        map.put(new User2("张三01", 12),11);
        //通过重写hashCode()和equals(  obj)方法防止重复的值存入
        Set set = map.keySet();
        for (  key : set) {
              value = map.get(key);
            System.out.println(key + ":" + value);
        }
    }
}

class User2{
    String name;
    int age;
    
    public User2(String name,int age){
        this.name=name;
        this.age=age;
    }
    
    @Override
    public int hashCode(){
        final int prime=31;
        int result=1;
        result=prime*result+age;
        result=prime*result+((name==null)?0:name.hashCode());
        return result;
    }
    @Override
    public boolean equals(  obj){
        if(this==obj)
            return true;
        if(obj==null)
            return false;
        if(getClass()!=obj.getClass())
            return false;
        User2 u=(User2) obj;
        if(age!=u.age)
            return false;
        if(name==null){
            if(u.name!=null)
                return false;
        }else if(!name.equals(u.name))
                return false;
        return true;
    }
    @Override
    public String toString() {
        return "User2 [name=" + name + ", age=" + age + "]";
    }
}
//比较器
class MyCompare implements Comparator{

    @Override
    public int compare(  o1,   o2) {
        if(o1 instanceof User2 && o2 instanceof User2){
            User2 u1=(User2) o1;
            User2 u2=(User2) o2;
            int sum=u1.age-u2.age;
            if(sum==0){
                return u1.name.compareTo(u2.name);
            }
            return sum;
        }
        throw new ClassCastException("不是User2 类型");
    }
    
}

User2 [name=张三01, age=10]:11
User2 [name=张三01, age=12]:11
User2 [name=张三02, age=13]:11