Reproducible Random Generation

Main.java

import org.apache.commons.lang3.reflect.FieldUtils;

import java.util.Random;
import java.util.concurrent.atomic.AtomicLong;

public class InvRand {

	static final String SEED_FIELD = "seed";

	public static void main(String[] args) throws IllegalAccessException {

		final Random r = new Random(122);
		final AtomicLong seed = getSeed(r);
		final int size = 10;
		final long[][] buffer = new long[size][2];

		// generating random numbers based on seed
		for (int i = 0; i < size; i++) {
			final long currSeed = seed.get();
			buffer[i][0] = nextInt(r, 0, 5);
			buffer[i][1] = currSeed;
			System.out.printf("n=%s, seed=%s%n", buffer[i][0], currSeed);
		}

		System.out.println("\n//======================================//\n");

		// replay generated numbers from seed
		for (int i = buffer.length - 1; i >= 0; i--) {
			final Random r2 = new Random();
			plainSetSeed(buffer[i], r2);
			for (int j = 0; j < size - i; j++) {
				final long currSeed = getSeed(r2).get();
				System.out.printf("index=%s, original{n=%s, seed=%s}, current{n=%s, seed=%s}%n", i + j, buffer[i + j][0], buffer[i + j][1], nextInt(r2, 0, 5), currSeed);
			}
			System.out.println();
		}
	}
	
	/**
	 * Returns a pseudo-random number between min and max, inclusive.
	 * The difference between min and max can be at most
	 * <code>Integer.MAX_VALUE - 1</code>.
	 *
	 * @param min Minimum value
	 * @param max Maximum value.  Must be greater than min.
	 * @return Integer between min and max, inclusive.
	 * @see java.util.Random#nextInt(int)
	 */
	public static int nextInt(Random r, int min, int max) {
		return r.nextInt((max - min) + 1) + min;
	}

	private static void plainSetSeed(long[] longs, Random r2) throws IllegalAccessException {
		FieldUtils.writeDeclaredField(r2, SEED_FIELD, new AtomicLong(longs[1]), true);
	}

	private static AtomicLong getSeed(Random r) throws IllegalAccessException {
		return (AtomicLong) FieldUtils.readField(r, SEED_FIELD, true);
	}
}