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;
	}

}