Question

Please note the print statements, in the code segments below. My question is how come If I try to add two doubles in the print statement it prints incorrectly, but if I add them outside the print statement and store the result in a variable than I am able to print it correctly.

Why does this work and print out the correct result?

public static void main(String argsp[]){
        Scanner input = new Scanner(System.in);

        double first, second, answer;

        System.out.println("Enter the first number: ");
        first = input.nextDouble();

        System.out.println("Enter the second number: ");
        second = input.nextDouble();

        answer = first + second;

        System.out.println("the answer is " + answer);

    }

Why does this print out the wrong result?

public static void main(String argsp[]){
        Scanner input = new Scanner(System.in);

        double first, second;

        System.out.println("Enter the first number: ");
        first = input.nextDouble();

        System.out.println("Enter the second number: ");
        second = input.nextDouble();

        System.out.println("the answer is " + first+second);

    }

Answer 1

It’s because what you’re basically doing in that second part is:

System.out.println("the answer is " + String.valueOf(first) + String.valueOf(second));

That’s how the compiler interprets it. Because the + operator when you are giving a String to a method is not a calculation but a concatenation.

If you want it done in one line, do it like this:

System.out.println("the answer is " + (first + second)); //Note the () around the calculation.