import org.contracts4j.*;
public class Calculator {
@Requires("num > 0")
@Ensures("result == num * 2")
public int doubleNumber(int num) {
return num * 2;
}
public static void main(String[] args) {
Calculator calculator = new Calculator();
int input = 5;
int result = calculator.doubleNumber(input);
System.out.println("Double of " + input + " is " + result);
}
}
