how to replace some character's of String
<p>I have a numeric String i want to change the String first three character's by another character</p>

<p>Suppose I have a String like  <code>0333XXXXXXX</code> and <code>+38333XXXXXXX</code>. if the first character of String is <code>+38</code> i want to replace it with "0" while remaining String remain the same Here is my code</p>

<pre><code>        private String modifyNumber(String num) {
                if (num.startsWith("+38")) {
                    num.replaceFirst("+38", "0");}
                   return num;}
</code></pre>

<p>"+38" is not accepting in <code>num.replaceFirst</code>.</p>