String replace method is not working
<pre><code>public static String capitalise(String str)
{
     if (str != null || !"".equals(str))
     {
         char chr=str.charAt(0);
         String check= Character.toString(chr);
         String check1= check.toUpperCase();
         char chr1=check1.charAt(0);
         str.replace(chr, chr1);
         return str;            
    }
    else
    {
         System.out.println("Not a valid String");
    }

    return str;
}
</code></pre>
