Java > Core Java Code Examples

DOS Calculator

``` DOS Calculator public class Calculator { public static abstract class Operation { private final String name; Operation(String name) { this.name = name; } public String toString() { return this.name; } // Perform arithmetic op represented by this constant abstract double eval(double x, double y); // Doubly nested anonymous classes public static final Operation PLUS = new Operation("+") { double eval(double x, double y) { return x + y; } }; public static final Operation MINUS = new Operation("-") { double eval(double x, double y) { return x - y; } }; public static final Operation TIMES = new Operation("*") { double eval(double x, double y) { return x * y; } }; public static final Operation DIVIDE = new Operation("/") { double eval(double x, double y) { return x / y; } }; } // Return the results of the specified calculation public double calculate(double x, Operation op, double y) { return op.eval(x, y); } } public class CalcTest { public static void main(String args[]) { double x = Double.parseDouble(args[0]); double y = Double.parseDouble(args[1]); operate(x, Calculator.Operation.PLUS, y); operate(x, Calculator.Operation.MINUS, y); operate(x, Calculator.Operation.TIMES, y); operate(x, Calculator.Operation.DIVIDE, y); } static void operate(double x, Calculator.Operation op, double y) { Calculator c = new Calculator(); System.out.println(x + " " + op + " " + y + " = " + c.calculate(x, op, y)); } } ```