Should I Close a Scanner Linked to System.in?

Closing a Scanner Linked to System.in

Closing a Scanner linked to System.in can be a quandary. While it is good coding practice to close open resources, doing so with a Scanner connected to System.in also closes System.in itself. This raises the question: is there a way to close the Scanner without affecting System.in?

Solution

The simplest solution is to refrain from closing the Scanner if you do not intend to close the underlying stream. In most cases, it is advisable to create a single Scanner that serves the entire program. This eliminates the need to repeatedly create and close it.

If for some reason you must close the Scanner, one option is to create a new Scanner instance with the same underlying stream. This separates the two entities and allows you to close the Scanner without affecting System.in.

Here's an example:

Scanner scanner = new Scanner(System.in);
// Use the scanner as needed...

// Create a new scanner with the same underlying stream.
Scanner newScanner = new Scanner(System.in);

// Close the first scanner.
scanner.close();

// Continue using the new scanner.
newScanner.nextInt();

// Close the second scanner.
newScanner.close();

This method ensures that System.in remains unaffected while allowing you to close the original Scanner.

It is important to note that creating multiple Scanner instances can have performance implications. If performance is a concern, it is best to use a single Scanner throughout the program's lifetime.

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