Bank.java

package com.javaMultithreading;

import java.util.concurrent.ConcurrentHashMap;

public class Bank {
	private ConcurrentHashMap<Integer, BankAccount> accounts = new ConcurrentHashMap<>();
	
	public void AddAccount(BankAccount account) {
		accounts.put(account.getAccountNumber(), account);
	}
	
	public BankAccount getAccount(int accNo) {
		return accounts.get(accNo);
	}
	
	public boolean transfer(int fromAcc, int toAcc, double amount) {
		BankAccount from = accounts.get(fromAcc);
		BankAccount to = accounts.get(toAcc);
		
		if(from == null || to == null)
			return false;
		
		BankAccount firstLock = fromAcc < toAcc ? from: to;
		BankAccount secondLock = fromAcc < toAcc ? to: from;
		
		firstLock.getLock().lock();
		secondLock.getLock().lock();
		
		try {
			if(!from.withdraw(amount)) return false;
			to.deposit(amount);
			System.out.println("Transferred"+amount+"from A/C"+fromAcc+"to A/C"+toAcc);
			return true;
		}
		finally {
			secondLock.getLock().unlock();
			firstLock.getLock().unlock();
		}
	}
	public void printAllBalances() {
		for(BankAccount acc: accounts.values()) {
			System.out.println("A/C"+acc.getAccountNumber()+"Balance: "+acc.getBalance());
		}
	}
}