Deadlock example caused by a incorrect nested synchronized block.

Bank.java

public class Bank {

  private String name; 
	
	
	public Bank(String name) {
		this.name = name;
	}
	
	public String getName() {
		return name;
	}
	
	@Override
	public boolean equals(Object obj) {
		Bank b = (Bank) obj;
		return b.getName().equals(name);
	}
}

BankAccount.java

public class BankAccount {

  private int balance;

	private Bank bank;

	public BankAccount(int balance) {
		this.balance = balance;
		this.bank = new Bank("Bank of GGC");
	}

	public synchronized void transfer(BankAccount target, int amount) throws DifferentBankException {
		if (!bank.equals(target.getBank()))
			throw new DifferentBankException();
		balance -= amount;
		synchronized (target) {
			target.balance += amount;
		}
	}

	public synchronized int balance() {
		return balance;
	}
	
	public Bank getBank() {
		return bank;
	}

}

BankAccountTransfer.java

public class BankAccountTransfer {

  public static void main(String[] args) throws DifferentBankException, InterruptedException {

		final BankAccount a = new BankAccount(10000);
		final BankAccount b = new BankAccount(10000);

		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				for (int i = 0; i < 1000; i++)
				{
					try {
						a.transfer(b, 10);
						System.out.println("Thread 1: " + i + " remaining: " + a.balance());
					} catch (DifferentBankException e) {
					}
				}
				System.out.println("Thread 1 done!");
			}
		});

		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				for (int i = 0; i < 1000; i++)
				{
					try {
						b.transfer(a, 10);
						System.out.println("Thread 2: " + i + " remaining: " + b.balance());
					} catch (DifferentBankException e) {
					}
				}
				System.out.println("Thread 2 done!");
				System.out.println(a.balance());
			}
		});

		t1.start();
		t2.start();

		Thread.sleep(100000);

	}
}

DifferentBankException.java

public class DifferentBankException extends Exception {

  public DifferentBankException() {

	}
	
	public DifferentBankException(String message) {
		super(message);
	}
}