How to immeditaly end program with J.option in Java if validation is not correct

Question

ane.showMessageDialog(null,"Error: Gender must be F or M") ;
}

  } else {
     //Write an error for invalid Age
     JOptionPane.showMessageDialog(null,"Erlll") ;  

  }






}//end main

 }//end class

Answer 1

Just move the code that asks for gender inside the if branch corresponding to an acceptable age:

public static void main (String[] args) { 

  final int DRINKING_AGE = 21;
  final int ADULT = 18;
  final String LEGAL_DRINKING_AGE_MESSAGE = "You are legally able to drink";

  int age = Integer.parseInt(JOptionPane.showInputDialog( "Enter Your Age"));

  boolean ageCheck = age >0 && age <=100;
  //check to see if the age is within range
  if (ageCheck) {
    String gender =  JOptionPane.showInputDialog( "Enter Your Gender (F/M)");
    boolean genderCheck = gender.equalsIgnoreCase("M")  || gender.equalsIgnoreCase("F");
     //check to see if the user entered M or F 
     if (genderCheck) {
           //if we pass both checks, then do the rest of the logic
           JOptionPane.showMessageDialog(null,"OUTPUT:  Your age is " + age + " and Gender is " + gender);

     } else { 
        //Write an error for invalid Gender
        JOptionPane.showMessageDialog(null,"Error:  Gender must be F or M") ;  
     }

  } else {
     //Write an error for invalid Age
     JOptionPane.showMessageDialog(null,"Error: Age must be between 0 -100") ;  

  }
}

If the logic gets any more complicated, I would suggest refactoring to isolate the logic for obtaining age and gender into separate methods. (I'd do it even for this code, but that's beyond the scope of what you asked about.)