修改hashset中對象的屬性值，且屬性值是計算哈希值的字段，這時會引起內存泄漏
即：當一個對象被存儲進HashSet集合中以后，就不能修改該對象的參與計算哈希值的屬性值了 ，否則對象修改后的哈希值與最初存儲進HashSet集合中時的哈希值就不同了，在這種情況下，即使在contains方法使用該對象的當前引用作為參數去HashSet集合中檢索對象，也將返回找不到對象的結果，這也會導致無法從HashSet集合中刪除當前對象，造成內存泄露。
舉例說明：
public class HashSetTest { public static void main(String[] args) { Set<Person> set = new HashSet<Person>(); Person p1 = new Person("唐僧", "pwd1", 25); Person p2 = new Person("孫悟空", "pwd2", 26); Person p3 = new Person("豬八戒", "pwd3", 27); set.add(p1); set.add(p2); set.add(p3); System.out.Word; private int age; public Person(String username, String password, int age) { this.username = username; this.password = password; this.age = age; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } 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 + ((password == null) ? 0 : password.hashCode()); result = prime * result + ((username == null) ? 0 : username.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; Person other = (Person) obj; if (age != other.age) return false; if (password == null) { if (other.password != null) return false; } else if (!password.equals(other.password)) return false; if (username == null) { if (other.username != null) return false; } else if (!username.equals(other.username)) return false; return true; } @Override public String toString() { return this.username + "-->" + this.password + "-->" + this.age; }}新聞熱點
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