import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class PrimeSearcher extends HttpServlet implements Runnable {
long lastprime = 0; // last prime found
Date lastprimeModified = new Date(); // when it was found
Thread searcher; // background search thread
public void init(ServletConfig config) throws ServletException {
super.init(config); // always!
searcher = new Thread(this);
searcher.setPriority(Thread.MIN_PRIORITY); // be a good citizen
searcher.start();
}
public void run() {
// QTTTBBBMMMTTTOOO
long candidate = 1000000000000001L; // one quadrillion and one
// Begin loop searching for primes
while (true) { // search forever
if (isPrime(candidate)) {
lastprime = candidate; // new prime
lastprimeModified = new Date(); // new "prime time"
}
candidate += 2; // evens aren't prime
// Between candidates take a 0.2 second break.
// Another way to be a good citizen with system resources.
try {
searcher.sleep(200);
}
catch (InterruptedException ignored) { }
}
}
private static boolean isPrime(long candidate) {
// Try dividing the number by all odd numbers between 3 and its sqrt
double sqrt = Math.sqrt(candidate);
for (long i = 3; i <= sqrt; i += 2) {
if (candidate % i == 0) return false; // found a factor
}
// Wasn't evenly divisible, so it's prime
return true;
}
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/plain");
PrintWriter out = res.getWriter();
if (lastprime == 0) {
out.println("Still searching for first prime...");
}
else {
out.println("The last prime discovered was " + lastprime);
out.println(" at " + lastprimeModified);
}
}
public void destroy() {
searcher.stop();
}
public long getLastModified(HttpServletRequest req) {
return lastprimeModified.getTime() / 1000 * 1000;
}
}
|