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

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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

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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());

}

}

}