Java using scanner enter key pressed

Question

I am programming using Java.
I am trying write code which can recognize if the user presses the enter key in a console based program.

How can I

Answer 1

This works using java.util.Scanner and will take multiple "enter" keystrokes:

    Scanner scanner = new Scanner(System.in);
    String readString = scanner.nextLine();
    while(readString!=null) {
        System.out.println(readString);

        if (readString.isEmpty()) {
            System.out.println("Read Enter Key.");
        }

        if (scanner.hasNextLine()) {
            readString = scanner.nextLine();
        } else {
            readString = null;
        }
    }

To break it down:

Scanner scanner = new Scanner(System.in);
String readString = scanner.nextLine();

These lines initialize a new Scanner that is reading from the standard input stream (the keyboard) and reads a single line from it.

    while(readString!=null) {
        System.out.println(readString);

While the scanner is still returning non-null data, print each line to the screen.

        if (readString.isEmpty()) {
            System.out.println("Read Enter Key.");
        }

If the "enter" (or return, or whatever) key is supplied by the input, the nextLine() method will return an empty string; by checking to see if the string is empty, we can determine whether that key was pressed. Here the text Read Enter Key is printed, but you could perform whatever action you want here.

        if (scanner.hasNextLine()) {
            readString = scanner.nextLine();
        } else {
            readString = null;
        }

Finally, after printing the content and/or doing something when the "enter" key is pressed, we check to see if the scanner has another line; for the standard input stream, this method will "block" until either the stream is closed, the execution of the program ends, or further input is supplied.

Answer 2

Scanner scan = new Scanner(System.in);
        int i = scan.nextInt();
        Double d = scan.nextDouble();


        String newStr = "";
        Scanner charScanner = new Scanner( System.in ).useDelimiter( "(\\b|\\B)" ) ;
        while( charScanner.hasNext() ) { 
            String  c = charScanner.next();

            if (c.equalsIgnoreCase("\r")) {
                break;
            }
            else {
                newStr += c;    
            }
        }

        System.out.println("String: " + newStr);
        System.out.println("Int: " + i);
        System.out.println("Double: " + d);

This code works fine