TreeSet中的排序问题——Comparable

package com.etc.hashset;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

public class TestHashSet {

/**
* @param args
*/
public static void main(String[] args) {

Set set=new TreeSet();
set.add(new Student("zhangsan",20));
set.add(new Student("zhangsan",20));
set.add(new Student("zhangsan5",29));
set.add(new Student("zhangsan3",25));
set.add(new Student("zhangsan7",27));
set.add(new Student("zhangsan1",21));

Iterator it = set.iterator();
int num=0;
while(it.hasNext()){
System.out.println(num+++"-"+it.next());
}
}
}

/**
* Comparable是专门用来对TreeSet和TreeMap进行排序用的，comparable是自然排序，所以在对象所在的类实现该接口即可，TreeSet就不需要再指定专门的构造器
*
*/

class Student implements Comparable {

@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;
}

//重写了该方法，用来判断是否是同一对象
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Student other = (Student) obj;
if (age != other.age)
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}

public Student() {

}

public Student(String name, int age) {
super();
this.name = name;
this.age = 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;
}

String name;
int age;

@Override
public int compareTo(Object o) {
if(o instanceof Student){
Student stu=(Student)o;
return this.age-stu.age;
}
return 0;
}

@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + "]";
}
}