title: String as immutable object
body: <p>If String is a immutable object then is it possible to revert the changed values back?
  What i mean is that if there is one string variable </p>
  
  <pre><code>String str="Hello";
  </code></pre>
  
  <p>and if it is changed to</p>
  
  <pre><code>str="Hi!";
  </code></pre>
  
  <p>Now, as we know that it will create two string objects "Hello" and "Hi!" and at present str points "Hi!". So what i am asking is that is it possible to assign reference of string "Hello"  <strong>(the previous one, not by creating new)</strong> to <strong>str</strong> as it is present somewhere in the memory?</p>