Java集合HashSet的hashcode方法引起的內存洩漏問題

1. package apistudy;
2. import java.util.HashSet;
3. import java.util.Set;
4. /**
5. * Created on 2010-6-7
6. * <p>Description: [HashSet的hashcode方法引起的內存洩漏]</p>
7. * @author [email protected]
8. * @version 1.0
9. */
10. public class HashSetTest
11. {
12. public static void main(String[] args)
13. {
14. Set<Person> set = new HashSet<Person>();
15. Person p1 = new Person("唐僧","pwd1",25);
16. Person p2 = new Person("孫悟空","pwd2",26);
17. Person p3 = new Person("豬八戒","pwd3",27);
18. set.add(p1);
19. set.add(p2);
20. set.add(p3);
21. System.out.println("總共有:"+set.size()+" 個元素!"); //結果：總共有:3 個元素!
22. p3.setAge(2); //修改p3的年齡,此時p3元素對應的hashcode值發生改變
23. set.remove(p3); //此時remove不掉，造成內存洩漏
24. set.add(p3); //重新添加，居然添加成功
25. System.out.println("總共有:"+set.size()+" 個元素!"); //結果：總共有:4 個元素!
26. for (Person person : set)
27. {
28. System.out.println(person);
29. }
31. }
32. }

運行結果：

總共有:3 個元素!

總共有:4 個元素!

豬八戒-->pwd3-->2

孫悟空-->pwd2-->26

唐僧-->pwd1-->25

豬八戒-->pwd3-->2

Person.java

1. package apistudy;
2. public class Person
3. {
4. private String username;
5. private String password;
6. private int age;
7. public Person(String username, String password, int age)
8. {
9. this.username = username;
10. this.password = password;
11. this.age = age;
12. }
13. public String getUsername()
14. {
15. return username;
16. }
17. public void setUsername(String username)
18. {
19. this.username = username;
20. }
21. public String getPassword()
22. {
23. return password;
24. }
25. public void setPassword(String password)
26. {
27. this.password = password;
28. }
29. public int getAge()
30. {
31. return age;
32. }
33. public void setAge(int age)
34. {
35. this.age = age;
36. }
37. @Override
38. public int hashCode()
39. {
40. final int prime = 31;
41. int result = 1;
42. result = prime * result + age;
43. result = prime * result + ((password == null) ? 0 : password.hashCode());
44. result = prime * result + ((username == null) ? 0 : username.hashCode());
45. return result;
46. }
47. @Override
48. public boolean equals(Object obj)
49. {
50. if (this == obj)
51. return true;
52. if (obj == null)
53. return false;
54. if (getClass() != obj.getClass())
55. return false;
56. Person other = (Person) obj;
57. if (age != other.age)
58. return false;
59. if (password == null)
60. {
61. if (other.password != null)
62. return false;
63. }
64. else if (!password.equals(other.password))
65. return false;
66. if (username == null)
67. {
68. if (other.username != null)
69. return false;
70. }
71. else if (!username.equals(other.username))
72. return false;
73. return true;
74. }
75. @Override
76. public String toString()
77. {
78. return this.username+"-->"+this.password+"-->"+this.age;
79. }
81. }