/*
 * File: Add2Integers.java
 * -----------------------
 * This program adds two integers and prints their sum.
 * This version defines its own implementation of readInt.
 *
 * Author: CS1MD3, Nov. 2008
 */

import acm.program.*;

public class Add2Integers extends ConsoleProgram {

   public void run() {
      println("This program adds two integers.");
      int n1 = myReadInt("Enter n1: ");
      int n2 = myReadInt("Enter n2: ");
      int total = n1 + n2;
      println("The total is " + total + ".");
   }

/**
 * Simulates readInt method.
 * @param prompt The prompt string
 * @return The integer read
 */

   private int myReadInt(String prompt) {
      while (true) {
         int value = 0;
         int sign = +1;
         String line = readLine(prompt);
         if (line.startsWith("-")) {
            sign = -1;
            line = line.substring(1);
         }
         int n = line.length();
         boolean okay = (n > 0);
         for (int i = 0; okay && i < n; i++) {
            char ch = line.charAt(i);
            if (Character.isDigit(ch)) {
               value = 10 * value + (ch - '0');
            } else {
               okay = false;
            }
         }
         if (okay) return sign * value;
         println("Illegal integer format");
      }
   }

}