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： 

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;  
    }  
  
}

 

 

 

原文地址： http://blog.csdn.net/aerchi/article/details/7921481