public class Student {

    private int studentId;

    private String studentName;

    private int age;

    public Student(int studentId , String studentName, int age){

        this.studentId=studentId;

        this.studentName=studentName;

        this.age=age;

    }

    public int getStudentId() {

        return studentId;

    }

    public void setStudentId(int studentId) {

        this.studentId = studentId;

    }

    public String getStudentName() {

        return studentName;

    }

    public void setStudentName(String studentName) {

        this.studentName = studentName;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

}

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

public class test {

    /**

     * @param args

     */

    public static void main(String[] args) {

        Comparator<Student> comparator = new Comparator<Student>() {

            public int compare(Student s1, Student s2) {

                // 先排年龄

                if (s1.getAge() != s2.getAge()) {

                    return s1.getAge() - s2.getAge();

                } else if (!s1.getStudentName().equals(s2.getStudentName())) {

                    // 年龄相同则按姓名排序

                    return s1.getStudentName().compareTo(s2.getStudentName());

                } else {

                    // 姓名也相同则按学号排序

                    return s1.getStudentId() - s2.getStudentId();

                }

            }

        };

         Student stu1 = new Student (1,"zhangsan",28);

         Student stu2 = new Student (2,"zhagnsan",19);

         Student stu3 = new Student (3,"wangwu",19);

         Student stu4 = new Student (4,"wangwu",19);

         Student stu5 = new Student (5,"zhaoliu",18);

          ArrayList<Student> list = new ArrayList<Student>();

          list.add(stu1);

          list.add(stu2);

          list.add(stu3);

          list.add(stu4);

          list.add(stu5);

          //这里就会自动根据规则进行排序

          Collections.sort(list,comparator);

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

              Student stu=list.get(i);

              System.out.println("年龄:"+stu.getAge()+"   姓名:"+stu.getStudentName()+"   学号:"+stu.getStudentId());

          }

    }

}

第二个是实现Comparable接口

public class Student2 implements Comparable<Student2>{  //必须实现CompareTo（）

    private int studentId;

    private String studentName;

    private int age;

    public Student2(int studentId , String studentName, int age){

        this.studentId=studentId;

        this.studentName=studentName;

        this.age=age;

    }

    public int getStudentId() {

        return studentId;

    }

    public void setStudentId(int studentId) {

        this.studentId = studentId;

    }

    public String getStudentName() {

        return studentName;

    }

    public void setStudentName(String studentName) {

        this.studentName = studentName;

    }

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public int compareTo(Student2 o) {

        if(age!=o.getAge()){

            return age-o.getAge();

        }else if(!studentName.equals(o.getStudentName())){

            return studentName.compareTo(o.getStudentName());

        }else {

            return studentId-o.getStudentId();

        }

    }

    @Override

    public boolean equals(Object obj) {

        if(obj instanceof Student2){

            Student2 stu=(Student2)obj;

            if((age==stu.getAge())&&(studentName.equals(stu.getStudentName()))&&(studentId==stu.getStudentId())){

                return true;

            }else

                return true;

        }else{

            return false;

        }

    }

}

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

public class test2 {

    /**

     * @param args

     */

    public static void main(String[] args) {

        Student2 stu1 = new Student2 (1,"zhangsan",28);

        Student2 stu2 = new Student2 (2,"zhagnsan",19);

        Student2 stu3 = new Student2 (3,"wangwu",19);

        Student2 stu4 = new Student2 (4,"wangwu",19);

        Student2 stu5 = new Student2 (5,"zhaoliu",18);

          ArrayList<Student2> list = new ArrayList<Student2>();

          list.add(stu1);

          list.add(stu2);

          list.add(stu3);

          list.add(stu4);

          list.add(stu5);

          //这里就会自动根据规则进行排序

          Collections.sort(list);

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

              Student2 stu=list.get(i);

              System.out.println("年龄:"+stu.getAge()+"   姓名:"+stu.getStudentName()+"   学号:"+stu.getStudentId());

          }

    }

}

结果：

年龄:18   姓名:zhaoliu   学号:5

年龄:19   姓名:wangwu   学号:3

年龄:19   姓名:wangwu   学号:4

年龄:19   姓名:zhagnsan   学号:2

年龄:28   姓名:zhangsan   学号:1

注：大家可以看下api文档里对接口 Comparable<T>接口的介绍，里面说是建议重写equals方法，否则可能出现怪异的表现