java的set对于重复数据的add操作

java对于重复的元素不是覆盖，而是直接忽略。这个是要注意下的。

public class Test {

	public static void main(String[] args) throws Exception {
		Set<User> set = new HashSet<User>();
		User user1 = User.valueOf("11", "22");
		User user2 = User.valueOf("11", "33");
		set.add(user1);
		set.add(user2);
		for (User user : set) {
			System.err.println(user.getName());
			System.err.println(user.getPassword());
		}

	}

}

public class User {
	private String name;
	private String password;

	public static User valueOf(String name, String password) {
		User user = new User();
		user.name = name;
		user.password = password;
		return user;
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == null || getName() == null) {
			return false;
		}
		User other = (User) obj;
		return other.getName().equals(getName());
	}

	@Override
	public int hashCode() {
		if (getName() == null) {
			return 0;
		}
		return getName().hashCode();
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

}

结果是：
11
22