集合-TreeSet-Comparable

Student类：name、age属性 
1 package com.bjpowernode.test01_set2_Comparable;
 /*
  * T: type
  */
 public class Student implements Comparable<Student> {
     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;
     }
     public Student(String name, int age) {
         super();
         this.name = name;
         this.age = age;
     }
     public Student() {
         super();
         // TODO Auto-generated constructor stub
     }
     /*@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(Object obj) {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())//判断两个“对象”的类型是否相同。
             return false;
         Student other = (Student) obj; //向下转型
         if (age != other.age)
             return false;
         if (name == null) {  //避免出现NullPointerException异常
             if (other.name != null)
                 return false;
         } else if (!name.equals(other.name))
             return false;
         return true;
     }*/
     /*
      * 当前对象与参数对象相同时返回 ： 0
      * 当前对象 大于参数对象 时： 1  正数
      *  当前对象 小于参数对象 时： -1 负数
      */
     @Override
     public int compareTo(Student s) {
         //按年龄排序，如果年龄相同，按姓名排序
         if(this.age == s.age){
             //按姓名排序， 调用字符串的compareTo
             return this.name.compareTo(s.name);
         }
         return this.age -s.age;
     }

 }

 TreeSet存储，遍历，排序输出
 1 package com.bjpowernode.test01_set2_Comparable;

 import java.util.TreeSet;
 /*
  * TreeSet中存放元素，默认按自然排序的方式去除重复项，并进行排序的
  * String和8种包装类中都指定自然排序方法：实现java.lang.Comparable接口，重写compareTo方法
  * 自定义的类放入TreeSet时，也实现实现java.lang.Comparable接口，重写compareTo方法
  */
 public class StudentTreeSetTest {
     public static void main(String[] args) {
         TreeSet<Student> tree = new TreeSet<>();
         Student s = new Student("Mike", 18);
         Student s1 = new Student("Join", 28);
         Student s3 = new Student("Join", 18);
         Student s4 = new Student("Smith", 18);
         tree.add(s);
         tree.add(s1);
         tree.add(s3);
         tree.add(s4);
         System.out.println(tree.size());
         System.out.println("姓名\t年龄");
         for (Student stu : tree) {
             System.out.println(stu.getName()+"\t"+stu.getAge());
         }
     }
 }