import java.io.*;
import java.math.*;
import java.util.*;

public class PrimeHandler extends Thread {
  private long lastPrime = 0;
  private String fileName = "last_prime.txt";
  private Date lastFound = new Date();
  private String password = "2isAnOddPrime";

  public static void main(String[] args) {
    new PrimeHandler();
  }

  public PrimeHandler() {
    //setDaemon(true);
    setPriority(Thread.MIN_PRIORITY); // be nice!
    start();
  }

  public String getPrime(String password) {
    if(password.equals(this.password))
      return "\nPrime: " + Long.toString(lastPrime) + "\nFound: " + lastFound;
    return "Wrong password!";
  }

  public void run() {
    long candidate = loadPrime();
     while(true) {
       if(isPrime(candidate)) {
         lastPrime = candidate;
         lastFound = new Date();
         savePrime(candidate);
       }
       candidate += 2;
       try { sleep(250); } catch(InterruptedException ie) {} // be nice!
    }        
  }

  private boolean isPrime(long candidate) {
    long sqrt = (long)Math.sqrt(candidate);
    for(long i = 3; i <= sqrt; i += 2)
      if(candidate % i == 0) return false;
    return true;
  }

  private synchronized void savePrime(long prime) {
    try {
      ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(fileName));
      oos.writeObject(new Long(prime));
      oos.close();
    } catch (IOException ioe) {}
  }

  private synchronized long loadPrime() {
    long prime = 3;
    try {
      ObjectInputStream ois = new ObjectInputStream(new FileInputStream(fileName));
      prime = ((Long)ois.readObject()).longValue();
      ois.close();
    } catch (Exception ioe) {}
    return prime;
  } 
}