JAVA之HashSet去重(本身无序不重复，针对对象去重)

桃扇骨 2022-05-24 11:24 190阅读 0赞

package yu;  
  
  
import java.util.HashSet;  
import java.util.Iterator;  
  
  
//无序不重复（但是对象要想不重复，要重写以下方法）  
  
  
public class Main \{  
public static void main(String\[\] args) \{  
  
HashSet<Student> set=new HashSet<>();  
  
Student stu1=new Student("yu1", "1");  
Student stu2=new Student("yu2", "2");  
Student stu3=new Student("yu3", "3");  
Student stu4=new Student("yu3", "3");//重复的对象  
  
set.add(stu1);  
set.add(stu2);  
set.add(stu3);  
set.add(stu4);  
  
//迭代器遍历  
Iterator<Student> it=set.iterator();  
while (it.hasNext()) \{  
Object obj = it.next();  
System.out.println(obj);  
\}  
\}  
\}  
class Student\{  
String name;

String id;

public Student(String name, String id) \{  
super();  
this.name = name;  
this.id = id;  
\}

@Override

//Java中所有的类都是继承于Object类,自带tostring方法,输出的是类名和内存首地址,

//通过重写toString方法,得到自己想要的打印结果

public String toString() \{

return id+":"+name;  
\}  
  
  
//通过重写这两个方法实现对象的去重（eclipse可自动生成）  
@Override  
public int hashCode() \{  
final int prime = 31;  
int result = 1;  
result = prime \* result + ((id == null) ? 0 : id.hashCode());  
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())  
return false;  
Student other = (Student) obj;  
if (id == null) \{  
if (other.id != null)  
return false;  
\} else if (!id.equals(other.id))  
return false;  
if (name == null) \{  
if (other.name != null)  
return false;  
\} else if (!name.equals(other.name))  
return false;  
return true;  
\}  
  
\}