### Question:
SymmetricKey extends AbstractKey implements Serializable, Hashable { public static byte[] xor(byte[] src, int value) { byte[] result = new byte[src.length]; for (int i = 0; i < src.length; i++) result[i] = (byte) ((src[i] ^ value) & 0xFF); return result; } SymmetricKey();  SymmetricKey(byte[] key);  SymmetricKey(byte[] key, KeyInfo keyInfo); static SymmetricKey fromPassword(String password, int rounds); static SymmetricKey fromPassword(String password, int rounds, byte[] salt); void setKey(byte[] key); byte[] getKey(); int getBitStrength(); int getSize(); @Override Map<String, Object> toHash(); @Override void updateFromHash(Map<String, Object> hash); byte[] encrypt(byte[] plaintext); byte[] decrypt(byte[] ciphertext); OutputStream encryptStream(OutputStream outputStream); InputStream decryptStream(InputStream inputStream); EtaEncryptingStream etaEncryptStream(OutputStream out); EtaDecryptingStream etaDecryptStream(InputStream in); byte[] etaEncrypt(byte[] data); byte[] etaSign(byte[] data); byte[] etaDecrypt(byte[] data); static byte[] xor(byte[] src, int value); @Override byte[] pack(); @Override boolean equals(Object obj); @Override int hashCode();  }### Answer:
@Test public void xor() throws Exception { byte[] test = new byte[]{0, 0x55, (byte) 0xFF}; byte[] src = new byte[]{0, 0x55, (byte) 0xFF}; test = SymmetricKey.xor(test, 0); assertArrayEquals(test, src); test = SymmetricKey.xor(test, 0xFF); assertArrayEquals(new byte[]{(byte) 0xFF, (byte) 0xAA, 0}, test); test = SymmetricKey.xor(src, 0x11); assertArrayEquals(new byte[]{0x11, (byte) 0x44, (byte) 0xEE}, test); }