List集合去除重复对象

对象重复是指对象里面的变量的值都相等，并不定是地址。list集合存储的类型是基础类型还比较好办，直接把list集合转换成set集合就会自动去除。

   当set集合存储的是对象类型时，需要在对象的实体类里面重写public boolean equals(Object obj) {} 和 public int hashCode() {} 两个方法。

  实体类

 public class Student {

 public String id;
 public String name;
 public Student() {
 }
 public Student(String id,String name) {
 this.id = id;
 this.name = name;
 }
 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;
 }
 @Override
 public boolean equals(Object obj) {
 Student s=(Student)obj;
 return id.equals(s.id) && name.equals(s.name);
 }
 @Override
 public int hashCode() {
 String in = id + name;
 return in.hashCode();
 }
 }

测试类

 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;

 public class QuSame {

     public static void main(String[] args) {
         List<Student> stu = new ArrayList<Student>();
         stu.add(new Student("1","yi"));
         stu.add(new Student("3","san"));
         stu.add(new Student("3","san"));
         stu.add(new Student("2","er"));
         stu.add(new Student("2","er"));
         //set集合保存的是引用不同地址的对象
         Set<Student> ts = new HashSet<Student>();
         ts.addAll(stu);

         for (Student student : ts) {
             System.out.println(student.getId()+"-"+student.getName());
         }
     }
 }