Listing 9.5, Calculator.java, is a simple command line calculator. Note that the

Question

Listing 9.5, Calculator.java, is a simple command line calculator. Note that the program terminates if any operand is nonnumeric. Write a program with an exception handler that deals with nonnumeric operands; then write another program without using an exception handler to achieve the same objective. Your program should display a message that informs the user of the wrong operand type before exiting. Example: Look at picture. Calculator.java: public class Calculator {   /** Main method */   public static void main(String[] args) {    // Check number of strings passed    if (args.length != 3) {    System.out.println(    "Usage: java Calculator operand1 operator operand2");    System.exit(0);    }
   // The result of the operation    int result = 0;
   // Determine the operator    switch (args[1].charAt(0)) {    case '+': result = Integer.parseInt(args[0]) +    Integer.parseInt(args[2]);    break;    case '-': result = Integer.parseInt(args[0]) -    Integer.parseInt(args[2]);    break;    case '*': result = Integer.parseInt(args[0]) *    Integer.parseInt(args[2]);    break;    case '/': result = Integer.parseInt(args[0]) /    Integer.parseInt(args[2]);    }
   // Display result    System.out.println(args[0] + ' ' + args[1] + ' ' + args[2]    + " = " + result);   } }

Explanation / Answer

a) add the following before your switch statement: try { Integer.parseInt(args[0]); } catch (NumberFormatException e) { System.out.println("Wrong Input: " + args[0]); System.exit(1); } try { Integer.parseInt(args[2]); } catch (NumberFormatException e) { System.out.println("Wrong Input: " + args[2]); System.exit(1); } b) add the following before your switch statement: for (char c : args[0].toCharArray()) { if ((int)c < 48 || (int)c > 57) { System.out.println("Wrong Input: " + args[0]); System.exit(1); } } for (char c : args[2].toCharArray()) { if ((int)c < 48 || (int)c > 57) { System.out.println("Wrong Input: " + args[2]); System.exit(1); } }

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