Long running methods from Java SDK for testing purposes
algorithm, concurrency, java
Solution
I've once used a public-private key generator to do something similar. This is a CPU intensive task. Doing it hundreds or thousands of times should give you a considerable delay.
Problem
I'm working through some tutorials and examples of java.util.concurrent package. Usually example authors put a placeholder marked with a comment 'long running task'. Since these examples are about concurrent programming I'm not keen of using Thread.sleep(long), surrounded by try-catch blocks. What do you use in these circumstances? To open an url, do some complicated float math, i/o... Optimally these long running tasks do not have any side effects. These methods can be seen as Loren Ipsums on the timescale. I'll add here concrete implementations: ``` import java.math.BigInteger; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.SecureRandom; import java.util.Random; public class LongRunningTasks { public void triggerKeyGeneration(int iterations) { try { long start = System.currentTimeMillis(); for (int i = 0; i < iterations; i++) { KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA", "SUN"); SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN"); keyGen.initialize(1024, random); keyGen.generateKeyPair(); } System.out.println("triggerKeyGeneration: " + (System.currentTimeMillis() - start)); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchProviderException e) { e.printStackTrace(); } } private static final int SCALE = 10000; private static final int ARRINIT = 2000; /** * http://www.codecodex.com/wiki/index.php?title=Digits_of_pi_calculation#Java * * @param digits - returns good results up to 12500 digits * @return */ public String piDigits(int digits){ StringBuffer pi = new StringBuffer(); int[] arr = new int[digits + 1]; int carry = 0; for (int i = 0; i <= digits; ++i) arr[i] = ARRINIT; for (int i = digits; i > 0; i-= 14) { int sum = 0; for (int j = i; j > 0; --j) { sum = sum * j + SCALE * arr[j]; arr[j] = sum % (j * 2 - 1); sum /= j * 2 - 1; } pi.append(String.format("%04d", carry + sum / SCALE)); carry = sum % SCALE; } return pi.toString(); } private static final Random rand = new Random(); private static final BigInteger veryBig = new BigInteger(1200, rand); public BigInteger nextProbablePrime() { return veryBig.nextProbablePrime(); } } ```