java 中对象比较大小

java 中对象比较大小

java 中对象比较大小有两种方法

1：实现Comparable 接口 的 public int compareTo(T o) 方法；

2：实现Comparator 接口 的 int compare(T o1, T o2)方法；

代码如下：

Java代码


import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

import java.util.Set;

import java.util.TreeSet;



public class Test {

public static void main(String[] args) {

List list =new ArrayList();

list.add(new Dept("2","研发部",23));

list.add(new Dept("2","总公司",575));

list.add(new Dept("2","总公司",565));

// Collections.sort(list);

Collections.sort(list, new Comparator(){



public int compare(Object arg0, Object arg1) {

// TODO Auto-generated method stub

Dept dept1=(Dept)arg0;

Dept dept2=(Dept)arg1;

return dept1.compareTo(dept2);

}



});



for (int i=0;i<list.size();i++){

System.out.println((Dept)list.get(i));

}





Dept dept1=new Dept("2","研发部",23);

Dept dept2=new Dept("2","kk",44);

Set set=new TreeSet(new Comparator(){



public int compare(Object arg0, Object arg1) {

// TODO Auto-generated method stub

return 0;

}



});

set.add(dept1);

set.add(dept2);





}

}



class Dept implements Comparable{

private String id;

private String name;

private long num;

public Dept(String id,String name,long num){

this.id=id;

this.name=name;

this.num=num;

}

public String getId() {

return id;

}



public void setId(String id) {

this.id = id;

}



public String getName() {

return name;

}



public void setName(String name) {

this.name = name;

}



public long getNum() {

return num;

}



public void setNum(long num) {

this.num = num;

}



public int compareTo(Object arg0) {

Dept dept=(Dept) arg0;

int i=0;

i=this.id.compareTo(dept.id);

if(i!=0){//部门id不相等

return i;

}else{//部门id相等

i=this.name.compareTo(dept.name);

if(i!=0){//部门名称不相等

return i;

}else{//部门名称不相等

if(this.num>dept.num)return 1;

else if(this.num<dept.num)return -1;

else return 0;

}

}



}

public String toString() {

// TODO Auto-generated method stub

return this.id+"-->"+this.name+"-->"+this.num;

}



}

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