without synchronized keyword

package HeadFirstJava;

class BankAccount {
private int balance = 100;

public int getBalance() {
return balance;
}
public void withdraw(int amount) {
balance = balance - amount;
}
}

class BobAndMonica implements Runnable {
private BankAccount account = new BankAccount();

public static void main(String[] args) {
BobAndMonica theJob = new BobAndMonica();
Thread one = new Thread(theJob);
Thread two = new Thread(theJob);
one.setName("Bob");
two.setName("Monica");
one.start();
two.start();
}
@Override
public void run() {
// TODO Auto-generated method stub
for (int x = 0; x < 10; x++) {
makeWithdrawl(10);
}
if (account.getBalance() < 0) {
System.out.println("Overdrawn");
}
}
private void makeWithdrawl(int amount) {
if (account.getBalance() >= amount) {
System.out.println(Thread.currentThread().getName() + " is about to withdraw");
try {
System.out.println(Thread.currentThread().getName() + " is going to sleep");
Thread.sleep(500);
} catch(InterruptedException ex) {ex.printStackTrace();}
System.out.println(Thread.currentThread().getName() + " woke up.");
account.withdraw(amount);
System.out.println(Thread.currentThread().getName() + " completes the withdrawl");
} else {
System.out.println("Sorry, not enough for " + Thread.currentThread().getName());
}
}

}

Bob is about to withdraw

Bob is going to sleep

Monica is about to withdraw

Monica is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Monica woke up.

Monica completes the withdrawl

Sorry, not enough for Monica

Sorry, not enough for Monica

Sorry, not enough for Monica

Sorry, not enough for Monica

OverdrawnBob is about to withdraw

Bob is going to sleep

Monica is about to withdraw

Monica is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Bob is about to withdraw

Bob is going to sleep

Monica woke up.

Monica completes the withdrawl

Monica is about to withdraw

Monica is going to sleep

Bob woke up.

Bob completes the withdrawl

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Sorry, not enough for Bob

Monica woke up.

Monica completes the withdrawl

Sorry, not enough for Monica

Sorry, not enough for Monica

Sorry, not enough for Monica

Sorry, not enough for Monica

Overdrawn