HashSet to store custom objects

• HashSet is a subclass of a subclass of class Collection collection set, the set of features within the storage element is 元素不可以重复, 无索引, 存储顺序不一致.

• The following code illustrates the use, HashSet object implements custom storage element not to repeat (override hashCode method and equls)

  import java.util.HashSet;
  
  public class HashSetDemo {
  	public static void main(String[] args) {
  		// 创建集合对象
  		HashSet<Student> hs = new HashSet<Student>();
  
  		// 创建学生对象
  		Student s1 = new Student("林青霞", 27);
  		Student s2 = new Student("柳岩", 22);
  		Student s3 = new Student("王祖贤", 30);
  		Student s4 = new Student("林青霞", 27);
  		Student s5 = new Student("林青霞", 20);
  		Student s6 = new Student("范冰冰", 22);
  
  		// 添加元素
  		hs.add(s1);
  		hs.add(s2);
  		hs.add(s3);
  		hs.add(s4);
  		hs.add(s5);
  		hs.add(s6);
  
  		// 遍历集合
  		for (Student s : hs) {
  			System.out.println(s.getName() + "---" + s.getAge());
  		}
  	}
  }
  

  • student class

  package cn.itcast_02;
  
  public class Student {
  	private String name;
  	private int age;
  
  	public Student() {
  		super();
  	}
  
  	public Student(String name, int age) {
  		super();
  		this.name = name;
  		this.age = age;
  	}
  
  	public String getName() {
  		return name;
  	}
  
  	public void setName(String name) {
  		this.name = name;
  	}
  
  	public int getAge() {
  		return age;
  	}
  
  	public void setAge(int age) {
  		this.age = age;
  	}
  
  	@Override
  	public int hashCode() {
  		final int prime = 31;
  		int result = 1;
  		result = prime * result + age;
  		result = prime * result + ((name == null) ? 0 : name.hashCode());
  		return result;
  	}
  
  	@Override
  	public boolean equals(Object obj) {
  		System.out.println(this + "---" + obj);
  		if (this == obj)
  			return true;
  		if (obj == null)
  			return false;
  		if (getClass() != obj.getClass())
  			return false;
  		Student other = (Student) obj;
  		if (age != other.age)
  			return false;
  		if (name == null) {
  			if (other.name != null)
  				return false;
  		} else if (!name.equals(other.name))
  			return false;
  		return true;
  	}
  
  }
  

• At this time, printing will not repeat again:
  Joey -30
  Bingbing -22
  LiuYan -22
  Brigitte -27
  Brigitte -20

• Original link:https://blog.csdn.net/qq_32059827/article/details/51580642