### Question:
Wallet { public Account getAccount(UscAddress addr) { synchronized (accessLock) { if (!accounts.containsKey(addr)) { return null; } if (unlocksTimeouts.containsKey(addr)) { long ending = unlocksTimeouts.get(addr); long time = System.currentTimeMillis(); if (ending < time) { unlocksTimeouts.remove(addr); accounts.remove(addr); return null; } } return new Account(ECKey.fromPrivate(accounts.get(addr))); } } Wallet(KeyValueDataSource keyDS); List<byte[]> getAccountAddresses(); String[] getAccountAddressesAsHex(); UscAddress addAccount(); UscAddress addAccount(String passphrase); UscAddress addAccount(Account account); Account getAccount(UscAddress addr); Account getAccount(UscAddress addr, String passphrase); boolean unlockAccount(UscAddress addr, String passphrase, long duration); boolean unlockAccount(UscAddress addr, String passphrase); boolean lockAccount(UscAddress addr); byte[] addAccountWithSeed(String seed); byte[] addAccountWithPrivateKey(byte[] privateKeyBytes); byte[] addAccountWithPrivateKey(byte[] privateKeyBytes, String passphrase);  }### Answer:
@Test public void getUnknownAccount() { Wallet wallet = WalletFactory.createWallet(); UscAddress addr = new UscAddress("0x0000000000000000000000000000000000000023"); Account account = wallet.getAccount(addr); Assert.assertNull(account); }