How to modify code that shows a data corruption problem

Question

I'm currently working on a project that shows me what a data corruption problem looks like. The output from the code (What is balance? 4) given below is incorrect since one task is overriding the task of another. I was wondering how I would be able to rewrite the code so that the balance is always 100.

import java.util.concurrent.*;

public class AccountWithoutSync {
  private static Account account = new Account();

  public static void main(String[] args) {
    ExecutorService executor = Executors.newCachedThreadPool(); //create thread pool

    // Create and launch 100 threads
    for (int i = 0; i < 100; i++) {
      executor.execute(new AddAPennyTask());
    }

    executor.shutdown();

    // Wait until all tasks are finished
    while (!executor.isTerminated()) {
    }

    System.out.println("What is balance? " + account.getBalance());
  }

  // A thread for adding a penny to the account
  private static class AddAPennyTask implements Runnable {
    public void run() {
      account.deposit(1);
    }
  }

  // An inner class for account
  private static class Account {
    private int balance = 0;

    public int getBalance() {
      return balance;
    }

    public void deposit(int amount) {
      int newBalance = balance + amount;

      // This delay is deliberately added to magnify the
      // data-corruption problem and make it easy to see.
      try {
        Thread.sleep(5);
      }
      catch (InterruptedException ex) {
      }

      balance = newBalance;
    }
  }
}