Java's Random PRG "seed" prediction. Ideone ready.

predict_java_random_seed.java

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    private static long multiplier = 0x5DEECE66DL;
    private static long addend = 0xBL;
    private static long mask = (1L << 48) - 1;

    public static void crack()
    {
        Random random = new Random();
        long v1 = random.nextInt();
        long v2 = random.nextInt();
        for (int i = 0; i < 65536; i++)
        {
            long seed = (long)v1 * 65536 + i;
            if ((((seed * multiplier + addend) & mask) >>> 16) == v2)
            {
                System.out.println("Seed found: " + seed);
                break;
            }
        }
    }

    public static void main (String[] args) throws java.lang.Exception
    {
        crack();
    }
}