Chapter 12, Problem 21E

Explanation of Solution

Program:

//Definition of class Test

public class Test

{

    //Definition of main method

    public static void main(String[] args) {

        //Call the method countBinary()

        countBinary(3);

    }

    //Definition of method countBinary()

    public static void countBinary(int n)

    {

        //Call the method countBinary()

        countBinary(n, "");

    }

    //Definition of method countBinary()

    private static void countBinary(int digitsLeft, String s)

    {

        //Check whether digitsLeft()

        if (digitsLeft == 0)

        {

            //Print the value

            System...