(Calculator) Revise Listing 1, Calculator.java, to accept an expression as a string in whi...

(Calculator) Revise Listing 1, Calculator.java, to accept an expression as a string in which the operands and operator are separated by zero or more spaces. For example, 3+4 and 3 + 4 are acceptable expressions. Here is a sample run:

LISTING 1 Calculator.java

1 public class Calculator {
2 /** Main method */
3 public static void main(String[] args) {
4 // Check number of strings passed
5 if (args.length != 3) {
6 System.out.println(
7 "Usage: java Calculator operand1 operator operand2");
8 System.exit(0);
9 }
10
11 // The result of the operation
12 int result = 0;
13
14 // Determine the operator
15 switch (args[1].charAt(0)) {
16 case '+': result = Integer.parseInt(args[0]) +
17 Integer.parseInt(args[2]);
18 break;
19 case '-': result = Integer.parseInt(args[0]) -
20 Integer.parseInt(args[2]);
21 break;
22 case '.': result = Integer.parseInt(args[0]) *
23 Integer.parseInt(args[2]);
24 break;
25 case '/': result = Integer.parseInt(args[0]) /
26 Integer.parseInt(args[2]);
27 }
28
29 // Display result
30 System.out.println(args[0] + ' ' + args[1] + ' ' + args[2]
31 + " = " + result);
32 }
33 }