first type: java.lang.String second type: int [duplicate]

Question

I don't know why I am getting this error of -first type: java.lang.String second type: int.... Its a basic calculator program using java

public static void  main(String[] args){
    System.out.println("Welcome to the calculator");

    Scanner input = new Scanner(System.in);
    System.out.println("Enter your first inter number: ");
    String k = input.next();
    System.out.println("Enter second inter number: ");
    String l = input.next();
    int a =Integer.valueOf(k);
    int b =Integer.valueOf(l);
    String prompt = "Enter 1 for addition, 2 for subtraction, 3 for multiplication," +
            " 4 for division, 5 for remainder between two numbers";
    System.out.println(prompt);
    int z = input.nextInt();
    if (z == 1){
        System.out.println("Addition of two numbers: "+a + b);}
    else if (z == 2){
        System.out.println("Subtraction of two numbers: " +a - b);}
    else if (z == 3){
        System.out.println("Multiplication of two numbers: "+a * b); }
    else if (z == 4){
        System.out.println("Division of two numbers: "+a / b);}
    else if (z == 5){
        System.out.println("remainder of two numbers: "+a % b);}
    else{
        System.out.println("Invalid input");

    }

}

The error is in :

else if (z == 2){
        System.out.println("Subtraction of two numbers: " +a - b);}

Answer 1

When you do "Subtraction of two numbers: " +a, Java concatenates the String and integer to form a String. Then, when it reaches the - b segment, it thinks you're trying to subtract an integer... from a String. If you put your math operations in parenthesis like this: (a - b) your code should work.