Transfer.java

package BankingAppThreads;


import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Transfers{
public static void main(String[] args) {
    BankAccount account1 = new BankAccount("12345-678", 500.00);
    BankAccount account2 = new BankAccount("98765-432", 1000.00);

    new Thread(new Transfer(account1, account2, 10.00), "Transfer1").start();
    new Thread(new Transfer(account2, account1, 55.88), "Transfer2").start();
}
}

class BankAccount {
private double balance;
private String accountNumber;
private Lock lock = new ReentrantLock();

BankAccount(String accountNumber, double balance) {
    this.accountNumber = accountNumber;
    this.balance = balance;
}

public boolean withdraw(double amount) {
    if (lock.tryLock()) {
        try {
            // Simulate database access
            Thread.sleep(100);
        }
        catch (InterruptedException e) {
        }
        balance -= amount;
        System.out.printf("%s: Withdrew %f\n", Thread.currentThread().getName(), amount);
        return true;
    }
    return false;
}

public boolean deposit(double amount) {
    if (lock.tryLock()) {
        try {
            // Simulate database access
            Thread.sleep(100);
        }
        catch (InterruptedException e) {
        }
        balance += amount;
        System.out.printf("%s: Deposited %f\n", Thread.currentThread().getName(), amount);
        return true;
    }
    return false;
}

public boolean transfer(BankAccount destinationAccount, double amount) {
    if (withdraw(amount)) {
        if (destinationAccount.deposit(amount)) {
            return true;
        }
        else {
            // The deposit failed. Refund the money back into the account.
            System.out.printf("%s: Destination account busy. Refunding money\n",
                    Thread.currentThread().getName());
            deposit(amount);
        }
    }

    return false;
}
}

class Transfer implements Runnable {
private BankAccount sourceAccount, destinationAccount;
private double amount;

Transfer(BankAccount sourceAccount, BankAccount destinationAccount, double amount) {
    this.sourceAccount = sourceAccount;
    this.destinationAccount = destinationAccount;
    this.amount = amount;
}

public void run() {
    while (!sourceAccount.transfer(destinationAccount, amount))
        continue;
    System.out.printf("%s completed\n", Thread.currentThread().getName());
}
}}