CODEWITHSUNDEEP
javastringintegermultiplication
AdamW
AdamW

Reputation: 63

Java Multiplying 2 integers from strings

I've tried searching a number of threads in terms of multiplying 2 strings. However, it seems that most of the links I found weren't applicable or I couldn't interpret them well enough.

Would it be possible if could tell me what is wrong with my current code?

public static void main(String[] args) {

    String sample = value1();
    String sample2 = value2();
            //========== Test if users placed any characters within the boxes =========\\
            try {
                Integer.parseInt(sample);
            } catch (NumberFormatException e) {
                System.out.println("System detects that you are using characters");
                return;
            }
            try {
                Integer.parseInt(sample2);
            } catch (NumberFormatException e) {
                System.out.println("System detects that you are using characters");
                return;
            }
     Integer.parseInt(sample); 
     Integer.parseInt(sample2);
    System.out.println("The total multiplication that you have inserted is "+sample * sample2+ ".");
}

public static String value1() { //obtain first user input. 

    String sample = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
    if (sample.isEmpty()) {

        JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
        sample = value1();


    }
    return sample;

}

public static String value2() { //obtain second user input. 

    String sample2 = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
    if (sample2.isEmpty()) {

        JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
        sample2 = value2();


    }
    return sample2;

}

}

My final output should multiply the following numbers

System.out.println("The total multiplication that you have inserted is "+sample * sample2+ ".");

Upvotes: 0

Views: 3520

Answers (4)

Nelly Vouzoukidou
Nelly Vouzoukidou

Reputation: 33

1st suggestion: Don't (ever!) declare 2 methods that do exactly the same thing!!

public static String value() { //obtain *first and second* user input. 
  String sample = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
  if (sample.isEmpty()) {
    JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
    sample = value();
  }
  return sample;
}

2nd suggestion: Don't check the validity of your input in both value() method and main():

public static int value() { //obtain second user input. 
  String sample = JOptionPane.showInputDialog(null, "Insert Value", "Enter amount ", JOptionPane.QUESTION_MESSAGE);
  if (sample.isEmpty()) {
    JOptionPane.showMessageDialog(null, "Error!", "No Value Detected", JOptionPane.ERROR_MESSAGE);
    return value();
  }
  try {
    int v = Integer.parseInt(sample);
    return v;
  } catch (NumberFormatException e) {
    System.out.println("System detects that you are using characters");
    return value();
  }
}

for this 2nd case, main becomes:

public static void main(String[] args) {
  int x1 = value();
  int x2 = value(); // call again the *same* method

  System.out.println("The total multiplication that you have inserted is "+x1 * x2+ ".");
}

Upvotes: 0

Christoph Giesche
Christoph Giesche

Reputation: 328

You have to assign the return value of Integer.parseInt() to variables. The variables passed as param stay unchanged.

 int a = Integer.parseInt(sample); 
 int b = Integer.parseInt(sample2);
 System.out.println("The total multiplication that you have inserted is " + a * b + ".");

Upvotes: 0

Rustam
Rustam

Reputation: 6515

you are trying to multiply two string not two number

you should use like this :

System.out.println("The total multiplication that you have inserted is "+ Integer.parseInt(sample) * Integer.parseInt(sample2)+ ".");

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1500865

You can't multiply strings together. You can multiply numbers, and it sounds like that's what you want to do. Indeed, you're already parsing the strings as integers - and then ignoring the result. You just need to change this:

 Integer.parseInt(sample); 
 Integer.parseInt(sample2);
 System.out.println("The total multiplication that you have inserted is "+sample * sample2+ ".");

to:

 int value1 = Integer.parseInt(sample); 
 int value2 = Integer.parseInt(sample2);
 System.out.println("The total multiplication that you have inserted is "
     + (value1 * value2) + ".");

Upvotes: 1

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