Here is a little refresher on concept of threads in Java

http://kamalmeet.com/java/multithreading-runnable-vs-thread/
http://kamalmeet.com/java/handling-multithreading-with-synchronization/
http://kamalmeet.com/java/synchronization-object-vs-class-level/

There can be times where you might want to give priority to one thread over another. Java provides you a way to do that by setting priority of threads.

Thread.setPriority

An Example

package com.kamalmeet;
public class TestThread {
	public static void main(String s[]) {
		RunnableTest r = new RunnableTest();
		for (int i = 0; i < 5; i++) {
			Thread t = new Thread(r);
			t.setName("t:" + i);
			t.setPriority(Thread.NORM_PRIORITY + i);
			t.start();
		}
	}
}

class RunnableTest implements Runnable {
	int count = 0;
	public synchronized void test() {
		try {
			count++;
			System.out.println(Thread.currentThread().getPriority());
			Thread.sleep(1000);
			//This will just introduce some delay 
			System.out.println(Thread.currentThread().getName() + " says Hello from Runnable:" + count);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	@Override
	public void run() {
		test();
	}
}

But there is a catch. Threads are handled at the operating system level, so Java is depending on OS to make sure thread priority is taken care of. Here is a good explanation of thread priority in Java being handled in different OS – http://www.javamex.com/tutorials/threads/priority_what.shtml