How can i make a loop for my code so it runs until user gives correct input?

Question

I am wondering how I could make this code loop whenever the user gives a number outside of what the operator variable is asking. I am open to different suggestions. I have tried and failed many times using the do while loop. I want the code to say "Choose a number between 1-4" if the user gives the wrong number and then I want the loop back to the operator variable until the user gives a correct number and after the correct answer is given I want the program to go though the rest of the code and close.

import static java.lang.System.*;
import static javax.swing.JOptionPane.*;
import static java.lang.Integer.*;


public class SimpleCalc {

  public static void main(String[] args) {



do { 

    String operator = showInputDialog("Choose operation: " + "\n" + 
                                      "[1] = Plus" + "\n" +
                                      "[2] = Minus" + "\n" + 
                                      "[3] = Multiply" + "\n" +
                                      "[4] = Divide" + "\n");
    int c = parseInt(operator);


if (c>4 || c<1) {
    showMessageDialog(null, "Choose a number between 1 - 4.");
} 

     else{
          String textA = showInputDialog("Enter first number: ");
          String textB = showInputDialog("Enter second number: ");
          int a = parseInt(textA);
          int b = parseInt(textB);

  switch(c) {
    case 1:
          showMessageDialog(null, a + " + " + b + " = " + (a+b));
      break;

    case 2:
          showMessageDialog(null, a + " - " + b + " = " + (a-b));
      break;

    case 3: 
          showMessageDialog(null, a + " * " + b + " = " + (a*b));
      break;

    case 4: 
          showMessageDialog(null, a + " / " + b + " = " + (a/b));
      break;
    }
   } 
  } while (c>4 || c<1);
 }
}

Answer 1

You are on the right track by using do while loop. However the value c is not seen as its within the do while block. if you add int c above the do block and make int c = parseInt(operator); to c = parseInt(operator); it will work

Answer 2

Move the declaration of c out of do block, otherwise it is not accessible in while

int c;

do {
        ...

        c = parseInt(operator);

        ...
} while (c > 4 || c < 1);