method - keep going

Question

import java.util.Scanner;
public class InteractiveRectangle
{
public static void main(String[] args)
{
    do 
    { 
        int length = readInteger ("For Length ");
        System.out.println();
        int width = readInteger ("For Width ");
        printRectangleDetails(length,width);// existing code goes here 
    } 
    while (keepGoing()); 

    System.out.println("Goodbye, friend"); 
}


/**
 * returns the details of the rectangle
 * @param height the height of the rectangle
 * @param width the width of the rectangle
 */
public static void printRectangleDetails (int length, int width)
{
    System.out.println ("This is the length of the rectangle " + length);

    System.out.println ("This is the width of the rectangle " + width);

    System.out.println (("This is the perimeter of the rectangle " + (length + width)));

    System.out.println (("This is the area of the rectangle " + (length * width)));
}

/**
 * Read in an integer and return its value
 * @param the prompt to be shown to the user
 */
public static int readInteger(String prompt)
{
    System.out.println (prompt);
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter an integer");

    while (!scan.hasNextInt()) // while non-integers are present
    {
        scan.next();
        System.out.println ("Bad input. Enter an integer.");
    }
    int input = scan.nextInt();
    return input;
}

/**
 * Read a positive integer and return its value
 * @param the prompt to be shown to the user
 */
public static int readPositiveInteger(String prompt)
{
    System.out.println (prompt);
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter an integer");
    boolean positive = false;

    while (scan.hasNextInt() && positive == false)
    {
        int input = scan.nextInt();
        if (input > 0)
        {
            positive = true;
            {
                return input;
            }
        }
        else
        {
            System.out.println ("Bad input enter an integer.");
            positive = false;
            scan.nextLine();

        }

    }
    return 0;
}

/**
 * Ask the user whether or not to spawn another rectangle
 * and returns the result as a boolean
 */
public static boolean keepGoing()    
{
    Scanner scan = new Scanner(System.in);
    boolean inputRead = false;
    boolean result = false;
    System.out.println ("Do you want to process another rectangle?"); 
    scan.next();
    String input = scan.next();

    if (input == "y")
    {
        inputRead = true;
        result = true;

    }
    else if (input == "n")
    {
        inputRead = true;
        result = false;

    }
    else
    {
        System.out.println("Bad input please try again!");
        scan.nextLine();
    }
    return result;

}

}

I want the program to ask the user if they want to spawn another rectangle, and keep going until the user answers this question with “n”. Atm when I run the program, the rectangle only spawns once, so I think there's a problem with my keepGoing method. Any help would be appreciated, Thanks!

Answer 1

Yes there are few problems: -

• First you are comparing strings using == operator, which will always be false. Use equals method: -

  if (input.equals("y"))   // or,   if (input.equalsIgnoreCase("y"))
  

• Secondly, you should not use scan.next() method, the way you are using. Your first scan.next should be assigned to input, as your 2nd scan.next contains the newline: -

  System.out.println ("Do you want to process another rectangle?"); 
  // scan.next();  // Should not be here.
  String input = scan.next();
  scan.next();     // Change the order
  

  Or, just use scan.nextLine(): -

  System.out.println ("Do you want to process another rectangle?"); 
  String input = scan.nextLine();
  

• Third, in your else part, you can just invoke your keepGoing method again, rather than reading input there: -

  else
  {
      System.out.println("Bad input please try again!");
      return keepGoing();
  }
  

• Also, in your if-else, rather than setting the boolean values to the variables, you can directly return from there.

So, in all, you can change your if-else if-else to: -

if (input.equals("y")) {
    return true;
}
else if (input.equals("n")) {
    return false;
}
else
{
    System.out.println("Bad input please try again!");
    return keepGoing();
}

And then, you don't need those boolean variables: - inputRead and result. Just remove them. And remove the return statement from the end of your method. As it will be unreachable code now.

Answer 2

This code:

if (input.equals("y"))
{
    inputRead = true;
    result = true;

}
else if (input.equals("n"))
{
    inputRead = true;
    result = false;

}

Should solve the problem. Remember, objects in Java are compared by references, not by values.

Answer 3

You are checking if two Strings are equal using == operator. Always, check String equality using equals method.

if (input == "y")

should be

if (input.equals("y"))

and in the rest of the places as well,

== operator checks if two String references point to the same String Object. equals method determines if two String objects are meaningfully equal.

Answer 4

always compare strings with .equals()

 if (input == "y")

replace to

 if (input.equals("y"))

Answer 5

if (input == "y")

always compare Strings with equals()

you need

if ("y".equals(input))

or

if ("y".equalsIgnoreCase(input)) // will also allow Y

change the other checks accordingly.