QuestionB.java

package Q16_23_Rand7_From_Rand5;

public class QuestionB {
	public static int rand7() {
		while (true) {
			int r1 = 2 * rand5(); /* evens between 0 and 9 */
			int r2 = rand5(); /* will be later used to generate a 0 or 1 */
			if (r2 != 4) { /* r2 has an extra even number, so discard the extra */
				int rand1 = r2 % 2; /* Generate 0 or 1 */
				int num = r1 + rand1; /* will be in the range 0 through 9 */
				if (num < 7) {
					return num;
				}
			}

		}
	}

	public static int rand5() {
		return (int) (Math.random() * 100) % 5;
	}

	public static void main(String[] args) {
		/* Test: call rand7 many times and inspect the results. */
		int[] arr = new int[7];
		int test_size = 1000000;
		for(int k = 0; k < test_size; k++){
			arr[rand7()]++;
		}
		
		for (int i = 0; i < 7; i++) {
			double percent = 100.0 * arr[i] / test_size;
			System.out.println(i + " appeared " + percent + "% of the time.");
		}
	}
}