HashSet()相关易错点

package homework_;

import java.util.HashSet;
import java.util.Objects;

/*
 *   @author  YAM
 */
public class Homework06 {
 public static void main(String[] args) {
  HashSet set = new HashSet();
  Perosn p1 = new Perosn(1001,"AA");
  Perosn p2 = new Perosn(1002,"BB");

  set.add(p1);
  set.add(p2);

  p1.name = "CC";//1

  set.remove(p1);//2

  System.out.println(set);
  set.add(new Perosn(1001,"CC"));//3

  System.out.println(set);

  set.add(new Perosn(1001,"AA"));//4
  System.out.println(set);

 }
}

class Perosn{
 public int age;
 public String name;

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

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

 @Override
 public boolean equals(Object o) {
  if (this == o) return true;
  if (o == null || getClass() != o.getClass()) return false;
  Perosn perosn = (Perosn) o;
  return age == perosn.age && Objects.equals(name, perosn.name);
 }

 @Override
 public int hashCode() {
  return Objects.hash(age, name);
 }
}

• output:

[Perosn{age=1002, name='BB'}, Perosn{age=1001, name='CC'}]
[Perosn{age=1002, name='BB'}, Perosn{age=1001, name='CC'}, Perosn{age=1001, name='CC'}]
[Perosn{age=1002, name='BB'}, Perosn{age=1001, name='CC'}, Perosn{age=1001, name='CC'}, Perosn{age=1001, name='AA'}]