True or False? and WHY??? Java HashSet Contains

import java.util.HashSet; 

public class MyClass
{
     public String s; 

     public MyClass(String s)
     {
         this.s = s;
     } 

     public int hashCode()
     {
         return s.hashCode();
     } 

     public boolean equals(Object obj)
     {
         if(obj == null)
             return false; 

         if(!(obj instanceof MyClass))
             return false; 

         MyClass other = (MyClass)obj;
         if(s == null)
         {
             return false;
         } 

         return(s.equals(other.s));
     } 

     public static void main(String[] args)
     {
         HashSet<MyClass> set = new HashSet<MyClass>(); 

         MyClass mc1 = new MyClass("a");
         set.add(mc1); 

         mc1.s = "b"; 

         MyClass mc2 = new MyClass("b"); 

         if(set.contains(mc2))
         {
             System.out.println("True");
         }
         else
         {
             System.out.println("False");
         }
     }
}

结果是False

我猜原因是： 

在向set存储时。位置是使用之前的哈希值得到的。 

之后改变了mc1.s使得其哈希值发生了变化。

调用contains方法时，找的是之后哈希值指向的位置。这是尽管mc1和mc2有同样的哈希值、且true == mc1.equeals(mc2)。但在该位置上根本没有存储东西，所以返回false 

  

另外刚才找到Set的API文档里有这么一段话 

Note: Great care must be exercised if mutable objects are used as set elements. The behavior of a set is not specified if the value of an object
is changed in a manner that affects equals comparisons while the object is an element in the set. 

  

这样结果是False或许就是由于HashSet的实现方法(用了哈希散列存储)~~