Simple example of the race condition in Java

ThreadSynchronisationDemo.java

public class ThreadSynchronisationDemo implements Runnable {
	
	private Account acct = new Account();

	public static void main(String[] args) {
		
		ThreadSynchronisationDemo r = new ThreadSynchronisationDemo();
		Thread one = new Thread(r);
		Thread two = new Thread(r);
		one.setName("Fred");
		two.setName("Lucy");
		one.start();
		two.start();
	}

	public void run() {
		for (int x = 0; x < 5; x++) {
			makeWithdrawal(10);
			if (acct.getBalance() < 0) {
				System.out.println("account is overdrawn!");
			}
		}
	}

	private /*synchronized*/ void makeWithdrawal(int amt) {

		if (acct.getBalance() >= amt) {

			System.out.println(Thread.currentThread().getName() + " is going to withdraw");

			try {

				Thread.sleep(500);

			} catch(InterruptedException ex) { }

			acct.withdraw(amt);

			System.out.println(Thread.currentThread().getName() + " completes the withdrawal");
		} else {
			System.out.println("Not enough in account for " +	Thread.currentThread().getName() + " to withdraw " +	acct.getBalance());
		}

	}

	class Account {
		private int balance = 50;
		public int getBalance() {
			return balance;
		}
		public void withdraw(int amount) {
			balance = balance - amount;
		}
	}
}