Member Avatar for divinity02

Write a program that will read two numbers and an integer code from the keyboard. The value of the integer code should be 1, 2, 3 or 4. If the value of the code is 1, compute the sum of the two numbers. If the code is 2, compute the difference (first minus second). If the code is 3, compute the product of the two numbers. If the code is 4, and the second number is not zero, compute the quotient (first divided by second). If the code is not equal to 1, 2, 3 or 4, display an error message. The program is then to display the two numbers, the integer code and the computed result to the screen.

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

        int num1, num2, code, sum;

        System.out.println("Please enter a number");
        num1 = read.nextInt();

        System.out.println("please enter second number");
        num2 = read.nextInt();

        System.out.println("please enter code");
        code = read.nextInt();


        if(code==1)
        {

          sum = 1 + 2;
        }

        if (code==2)
        {

           sum = 1 - 2;

        }
        if(code ==4)
        {

          sum = 1 / 2;

        }

        else if (code!=1,2,3,4); - I am getting an error and can you tell me if I have code this correctly
        {

            System.out.println("Print error");

        }

can somebody tell if I have use the right code for this problem but I write it as i see it but I can be wrong.

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Generated

Quick diagnosis of the posted code: the program reads two inputs but then uses literal numbers for the calculations, the conditional structure is malformed (the comma and trailing semicolon make the "else if" into a syntax error), and the separate plain if statements mean more than one branch could run. Also, using integer types for division can give integer division results and there is no check for division by zero. Those points echo what , and hinted at, but a concrete, safe pattern will make the intent obvious and avoid compile/runtime surprises.

A clear, robust approach:

  • Read the two numbers into floating-point variables so division behaves as expected.
  • Read the operation code as an int.
  • Use a switch (or an else-if chain) so only one branch runs.
  • For division, check the second input for zero before dividing.
  • Print the two inputs, the code and the computed result (or an error message) and exit early on invalid input so nothing uninitialized gets printed.

Example corrected program:

import java.util.Scanner;

public class Calc {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double a, b, result = Double.NaN;
        int code;

        System.out.print("First number: ");
        a = in.nextDouble();
        System.out.print("Second number: ");
        b = in.nextDouble();
        System.out.print("Code (1-4): ");
        code = in.nextInt();

        switch (code) {
            case 1: result = a + b; break;
            case 2: result = a - b; break;
            case 3: result = a * b; break;
            case 4:
                if (b == 0) { System.out.println("Error: division by zero"); in.close(); return; }
                result = a / b;
                break;
            default:
                System.out.println("Error: invalid code"); in.close(); return;
        }

        System.out.printf("first=%s second=%s code=%d result=%s%n", a, b, code, result);
        in.close();
    }
}

Quick troubleshooting notes: remove stray semicolons after if/else, do not use commas to combine conditions, and handle InputMismatchException if non-numeric input is possible. Testing with edge cases (code outside 1-4, second number zero, decimal inputs) will confirm behavior.

Recommended Answers

All 3 Replies

Member Avatar for hericles

If you wanted to go with the IF statement there you would need to include each IF separately.
else if(code != 1 && code != 2 && code != 3 && code != 4)
Of course, once you've done IFs for 1,2,3,4 you don't need to do that, a simple ELSE {} will work because there are no other values you're interested in. NOTE: you'd need to change your other IFs (except the first one) to ELSE IF for that to work.

Member Avatar for stultuske

how is this
sum = 1 + 2;
working out for you ? what's the use of reading values if you're not going to use those ?

Member Avatar for Slavi

I'd also include that for my own preferences I'd go for what @herices said but with more brackets for clear reading
else if((code != 1) && (code != 2) && (code != 3) && (code != 4))

Next thing, you should probably check whether the number is between 1-4 first before executing the if statements, in other words you can start with an if statement such as
if((code != 1) && (code != 2) && (code != 3) && (code != 4))
then print error,
else()
include all your code in here for the rest

Next you are not using the numbers you get from the user? Do you mean by your 1 and 2 to have the user number 1 and user number 2? If so, fix it ... Also, this is what meant

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