Answer by Morsu for What is a race condition?

Try this basic example for better understanding of race condition:

    public class ThreadRaceCondition {    /**     * @param args     * @throws InterruptedException     */    public static void main(String[] args) throws InterruptedException {        Account myAccount = new Account(22222222);        // Expected deposit: 250        for (int i = 0; i < 50; i++) {            Transaction t = new Transaction(myAccount,                    Transaction.TransactionType.DEPOSIT, 5.00);            t.start();        }        // Expected withdrawal: 50        for (int i = 0; i < 50; i++) {            Transaction t = new Transaction(myAccount,                    Transaction.TransactionType.WITHDRAW, 1.00);            t.start();        }        // Temporary sleep to ensure all threads are completed. Don't use in        // realworld :-)        Thread.sleep(1000);        // Expected account balance is 200        System.out.println("Final Account Balance: "+ myAccount.getAccountBalance());    }}class Transaction extends Thread {    public static enum TransactionType {        DEPOSIT(1), WITHDRAW(2);        private int value;        private TransactionType(int value) {            this.value = value;        }        public int getValue() {            return value;        }    };    private TransactionType transactionType;    private Account account;    private double amount;    /*     * If transactionType == 1, deposit else if transactionType == 2 withdraw     */    public Transaction(Account account, TransactionType transactionType,            double amount) {        this.transactionType = transactionType;        this.account = account;        this.amount = amount;    }    public void run() {        switch (this.transactionType) {        case DEPOSIT:            deposit();            printBalance();            break;        case WITHDRAW:            withdraw();            printBalance();            break;        default:            System.out.println("NOT A VALID TRANSACTION");        }        ;    }    public void deposit() {        this.account.deposit(this.amount);    }    public void withdraw() {        this.account.withdraw(amount);    }    public void printBalance() {        System.out.println(Thread.currentThread().getName()+" : TransactionType: "+ this.transactionType +", Amount: "+ this.amount);        System.out.println("Account Balance: "+ this.account.getAccountBalance());    }}class Account {    private int accountNumber;    private double accountBalance;    public int getAccountNumber() {        return accountNumber;    }    public double getAccountBalance() {        return accountBalance;    }    public Account(int accountNumber) {        this.accountNumber = accountNumber;    }    // If this method is not synchronized, you will see race condition on    // Remove syncronized keyword to see race condition    public synchronized boolean deposit(double amount) {        if (amount < 0) {            return false;        } else {            accountBalance = accountBalance + amount;            return true;        }    }    // If this method is not synchronized, you will see race condition on    // Remove syncronized keyword to see race condition    public synchronized boolean withdraw(double amount) {        if (amount > accountBalance) {            return false;        } else {            accountBalance = accountBalance - amount;            return true;        }    }}