关于重写对象的hashCode方法和equals方法后HashMap还是可以重复的问题

class User {
private String name;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public User(String name) { super(); this.name = name; }
@Override public int hashCode() { return 2 * name.hashCode(); }
public boolean equals(Object user) { if (this.getName().equals(((User) user).getName())) { return true; } else return false; }
@Override public String toString() { return “User [name=” + name + “]”; }