os assignment: java thread

ThreadTester.java

// https://repl.it/@Gumball12/os-assignment-java-thread

// import modules
import java.lang.Thread;
import java.lang.Math;
import java.lang.InterruptedException;

// ThreadTester class
public class ThreadTester {
  public static void main (String[] args) {
    // create PrintThread instances with name
    PrintThread pt1 = new PrintThread("thread1");
    PrintThread pt2 = new PrintThread("thread2");
    PrintThread pt3 = new PrintThread("thread3");

    System.out.println("Starting threads");

    // starting threads
    pt1.start();
    pt2.start();
    pt3.start();

    System.out.println("Threads started, main ends\n");

    // main-thread end
  }
}

// PrintThread class
class PrintThread extends Thread {
  // sleep time
  private int sleep;

  // constructor
  public PrintThread (String name) {
    super(name);
    sleep = (int) (Math.random() * 5001);
  }

  // thread run
  public void run () {
    try {
      System.out.println(getName() + " going to sleep for " + sleep + " ms");
      Thread.sleep(sleep); // sleep
    } catch (InterruptedException ex) {
      ex.printStackTrace();
    }

    System.out.println(getName() + " done sleeping");\

    // sub-thread end
  }
}