Java Thread creation time increases with the number of Threads created. Little more description can be found at http://mtktechiecode.blogspot.in/2014/01/java-analyzing-thread-creation-time.html

ThreadCreationTimeIncreasesWithNumberOfThreads.java

public class ThreadCreationTimeIncreasesWithNumberOfThreads {
  public static void main(String[] args) {
    long threadCreationTime = 0, noOfThreadsCreated=1;
    while (true) {
      long time = System.currentTimeMillis();
      new Thread() {
          public void run() {}
      }.start();
      time = System.currentTimeMillis() - time;
      if (time > threadCreationTime) {
        System.out.println(noOfThreadsCreated + " numbered thread created in " + time + "ms.");
        threadCreationTime = time;
      }
      noOfThreadsCreated++;
    }
  }
}