Exercise 14: Calculator

This exercise is about building a mini calculator program. The program is supposed to take two numbers with an operator in between and do the requested sum. The program tests the operator against each of the standard ones +, -, *, or /.

// Calculate an integer sum using one of the four standard operators. class Calculator { public static void main(String[] args) { Calculator program = new Calculator(); if (args.length != 3) { System.err.println("Usage: java Calculator x op y"); System.exit(1); } program.sum(args[0], args[1], args[2]); } void sum(String s1, String op, String s2) { int x = Integer.parseInt(s1); int y = Integer.parseInt(s2); int z = 0; System.out.println("" + x + op + y + "=" + z); } }

In case the operating system treats any of the operators as special characters, the operator will need to have quotes round it, e.g. java Calculator 3 "+" 4 but the quotes will be taken off by the operating system before the arguments reach your program, so the program itself does not need to take account of the quotes.

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