public void equals(Object o){
 if(this == o) retun true;
 if(!(o instanceof Student)) return false;
 Student stu = (Studend)o;
 if(id!=stu.id) return false;
 if(age!=stu.age) return false;
 return name!=null ? name.equals(stu.name) : stu.name ==null; 
}

public int hashCode(){
 int result = id;
 reuslt = 31*id +(name!=null?name.hashCode():0);
 reuslt = 31*age;
 return reuslt;
}

package com.test.arithmetic.listequals;

/**
 * 这里id，name,age相同则Student相同，
 * 若有其他相同
 * Created by Administrator on 2016/3/29.
 */
public class Student {
 int id;
 String name;
 int age;

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

 @Override
 public boolean equals(Object o) {
  if (this == o) return true;
  if (!(o instanceof Student)) return false;

  Student student = (Student) o;

  if (id != student.id) return false;
  if (age != student.age) return false;
  return name != null ? name.equals(student.name) : student.name == null;

 }

 @Override
 public int hashCode() {
  int result = id;
  result = 31 * result + (name != null ? name.hashCode() : 0);
  result = 31 * result + age;
  return result;
 }

}

package com.test.arithmetic.listequals;
import org.junit.Assert;

import java.util.*;

/**
 * 取出list中重复的Student对象
 * Created by Administrator on 2016/3/29.
 */
public class ObtainListEquals {
 public static void main(String[] args){
  //原始数据
  List<Student> list = new ArrayList<>();
  //重复数据
  List<Student> list2 = new ArrayList<>();
  //填充
  for (int i = 0; i < 10 ; i++) {
   list.add(new Student(i,"_"+i,18+i));
   Random random = new Random();
   if (random.nextBoolean()){
    list.add(new Student(i,"_"+i,18+i));
   }
  }
  //使用hashset去重复，set为重复的集合，可以通过new ArrayList(set)转换成list
  HashSet<Student> set = new HashSet<>();
  for (Student student : list) {
   boolean add = set.add(student);
   if (!add){
    list2.add(student);
   }
  }
  //比较
  Assert.assertEquals(list.size(),list2.size()+set.size());
  
 }

}

package com.test.arithmetic.listequals;

/**
 * 这里id，name,age相同则Student相同，
 * 若有其他相同
 * Created by Administrator on 2016/3/29.
 */
public class Student implements Comparable<Student>{
  int id;
  String name;
  int age;

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

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof Student)) return false;

    Student student = (Student) o;

    if (id != student.id) return false;
    if (age != student.age) return false;
    return name != null ? name.equals(student.name) : student.name == null;

  }

  @Override
  public int hashCode() {
    int result = id;
    result = 31 * result + (name != null ? name.hashCode() : 0);
    result = 31 * result + age;
    return result;
  }

  @Override
  public int compareTo(Student o) {
    return this.id-o.id;
  }
}

package com.test.arithmetic.list.sort;

import com.test.arithmetic.list.Student;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * 对list中对象排序
 * Created by Administrator on 2016/3/29.
 */
public class SortList {
  List<Student> list;
  @Before
  public void setUp(){
    list = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
      int v = (int)(Math.random() * 100);
      list.add(new Student(v,"_"+v,18+v));
    }
    System.out.println("原list："+list);
  }
  //方法一，对象实现Comparable接口
  @Test
  public void byImplements(){
    Collections.sort(list);
    System.out.println("排序后："+list);
  }
}

package com.test.arithmetic.list;

/**
 * 这里id，name,age相同则Student相同，
 * 若有其他相同
 * Created by Administrator on 2016/3/29.
 */
public class Student{
  int id;
  String name;
  int age;

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

  public int getId() {
    return id;
  }

  public Student(int id) {
    this.id = id;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof Student)) return false;

    Student student = (Student) o;

    if (id != student.id) return false;
    if (age != student.age) return false;
    return name != null ? name.equals(student.name) : student.name == null;

  }

  @Override
  public int hashCode() {
    int result = id;
    result = 31 * result + (name != null ? name.hashCode() : 0);
    result = 31 * result + age;
    return result;
  }

  @Override
  public String toString() {
    return "Student{" +
        "id=" + id +
        ", name='" + name + '\'' +
        ", age=" + age +
        '}';
  }
}

package com.test.arithmetic.list.sort;

import com.test.arithmetic.list.Student;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * 对list中对象排序
 * Created by Administrator on 2016/3/29.
 */
public class SortList {
  List<Student> list;
  @Before
  public void setUp(){
    list = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
      int v = (int)(Math.random() * 100);
      list.add(new Student(v,"_"+v,18+v));
    }
    System.out.println("原list："+list);
  }
  //方法一，对象实现Comparable接口
  @Test
  public void byImplements(){
//    Collections.sort(list);
    System.out.println("排序后："+list);
  }

  /*方法二，添加比较器*/
  @Test
  public void byOverideCompare(){

    Collections.sort(list, new Comparator<Student>() {
      @Override
      public int compare(Student o1, Student o2) {
        return o1.getId()-o2.getId();
      }
    });
    System.out.println(list);
  }
}