How do I use a delimiter on an already-scanned String without declaring another Scanner object?

Question

For a program I'm writing, I need to read in a user-inputted time with the format HH:MM:SS AM (or PM). The program must exit when the user types "quit". I must use a delimiter to initialize the hours, minutes, seconds, and AM/PM variables from the user-inputted String.

In order to check that the user did not type "quit" I first read in the String and did a standard check using the equalsIgnoreCase("quit") method. However, I need to be able to use a delimiter on the String if the "quit" check passes. Since my initial scanner is reading input from the System.in stream, how would I use a delimiter on the String I have already read in without creating another Scanner object like this: Scanner input = new Scanner(s).useDelimiter(":|\\s+");?

My code is below:

import java.util.Scanner;

public class Delimiter
{
    public static void main(String[] args)
    {
        int hours, minutes, seconds = 0;
        String ampm, s = "";

        Scanner scan = new Scanner(System.in);

        while (true)
        {
            s = scan.nextLine();   //scans input
            if (s.equalsIgnoreCase("quit"))  //checks if input is "quit"
            {
                System.out.println("Exiting program.");  
                return;        //exits method
            }
            else 
            {
                Scanner input = new Scanner(s).useDelimiter(":|\\s+");  //This is what I want to avoid
                hours = input.nextInt();
                minutes = input.nextInt();
                seconds = input.nextInt();
                ampm = input.nextLine().trim();
            }

            System.out.println("Hours = " + hours);
            System.out.println("Minutes = " + minutes);
            System.out.println("Seconds = " + seconds);
            System.out.println("Morning or Afternoon = " +ampm);
        }
    }
}

Closing `System.in` at the end of a console application is not necessary, and also not useful. I don't understand why people keep saying you should close `System.in`; nobody has the same belief about `System.out`. The JVM opened it, so the JVM will close it, too. — kaya3, Mar 02 '20 at 21:51
Closing `System.in` is the only effect of calling `close()` on the Scanner in this code. — kaya3, Mar 02 '20 at 21:57
That one doesn't hold a reference to any closeable resource, so calling `close()` on it has no effect at all. It sets a boolean flag internally in the Scanner that is going to be garbage-collected anyway. See the [source](http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/8cc500af2454/src/share/classes/java/util/Scanner.java#l1120) if you are unconvinced. — kaya3, Mar 02 '20 at 22:01
Or it does harm like closing `System.in` before you are actually finished with it, leading to questions like [this one](https://stackoverflow.com/questions/14142853/close-a-scanner-linked-to-system-in) and [this one](https://stackoverflow.com/questions/14962082/close-scanner-without-closing-system-in) where the askers think it's necessary to call `Scanner.close()` even though they actually don't want anything to be closed, and the answers obligingly offer ways to make `Scanner.close()` do nothing so that it can be called with no effect. — kaya3, Mar 02 '20 at 22:13

Koray Tugay · Answer 1 · 2020-03-04T21:35:10.473

How about something like this? Does this help?

import java.util.Scanner;

public class Delimiter {
    public static void main(String[] args) {
        int hours, minutes, seconds;
        String ampm;

        Scanner scan = new Scanner(System.in);

        while (true) {
            String s = scan.nextLine();
            if ("quit".equalsIgnoreCase(s))
                break;

            String[] split = s.split(":|\\s+");
            hours = Integer.parseInt(split[0]);
            minutes = Integer.parseInt(split[1]);
            seconds = Integer.parseInt(split[2]);
            ampm = split[3];
        }

        System.out.println("Exiting program.");
    }
}

I am sure there can be other approaches, but what you have does not look so bad either. Why do you want to avoid the second Scanner?

That's an interesting solution. I'll have to try it later to see how that works. I've read that opening multiple scanner objects in a program is not a good idea and can lead to problems down the road in larger programs, so I wanted to see if there were better ways to accomplish what I want to do without opening a second scanner. — Jonathan, Mar 02 '20 at 22:00

How do I use a delimiter on an already-scanned String without declaring another Scanner object?

1 Answers1