Synchronization in java

package com.cp;

public class ThreadApply {
	
	public int iCount=0;
	
	public ThreadApply(){
		Thread1 t1 = new Thread1("thread 1"); // ++
		Thread2 t2 = new Thread2("thread 2"); // --
	}
	
	
	
	public static void main(String... args) {
		new ThreadApply();
	}
	
	
	private class Thread1 extends Thread {
		Thread1(String s) {
			super(s);
			start();
		}
	
		public synchronized void run() {
			for (int i = 0; i < 200; i++) {
				iCount++;
				System.out.println(Thread.currentThread().getName() + " iCount:" + iCount);
				try {
//					Thread.sleep(1000); // no sleeping for you, Mr. Thread1
				} catch (Exception e) {
				}
			}
		}
	}
	
	private class Thread2 extends Thread {
		Thread2(String s) {
			super(s);
			start();
		}
	
		public void run() {
			sum();
		}
	
		public synchronized void sum() {
			for (int i = 0; i < 20; i++) {
				iCount--;
				System.out.println("\t"  + Thread.currentThread().getName() + " iCount:" + iCount);
				try {
					Thread.sleep(100);
				} catch (Exception e) {
				}
			}
		}
	}


}