public class ParseInt
{
   public static void main(String[] args)
   {
      String a = "12";
      String b = "34";


      System.out.println( a + b );
                // a + b = "12" + "34" = "1234" 
                // Because + = concatenate when used on strings

      System.out.println( Integer.parseInt(a) + Integer.parseInt(b) );
                // Integer.parseInt(a) + Integer.parseInt(b)
                // = Integer.parseInt("12") + Integer.parseInt("34")
                // = 12 + 34 = 46
                // Because + = ADD when used on integers
   }
}