### Question:
TrieImpl implements Trie { public static byte[] bytesToKey(byte[] bytes) { int factor = 8; int mask = 0x01; int nbits = 1; byte[] keyBytes = new byte[bytes.length * factor]; int l = bytes.length; int j = 0; for (int k = 0; k < l; k++) { byte b = bytes[k]; for (int i = 0; i < factor; i++) { keyBytes[j++] = (byte) ((b >> (nbits * (factor - i - 1))) & mask); } } return keyBytes; } TrieImpl();  TrieImpl(boolean isSecure);  TrieImpl(TrieStore store, boolean isSecure); private  TrieImpl(TrieStore store, byte[] encodedSharedPath, int sharedPathLength, byte[] value, boolean isSecure); private  TrieImpl(byte[] encodedSharedPath, int sharedPathLength, byte[] value, TrieImpl[] nodes, Keccak256[] hashes, TrieStore store); @Override Trie cloneTrie(); @Override Trie cloneTrie(byte[] newValue); @Override void removeNode(int position); @Override void removeValue(); static TrieImpl fromMessage(byte[] message, TrieStore store); @Override Keccak256 getHash(); @Override byte[] get(byte[] key); @Override byte[] get(String key); @Override Trie put(byte[] key, byte[] value); @Override Trie put(String key, byte[] value); @Override Trie delete(byte[] key); @Override Trie delete(String key); @Override byte[] toMessage(); @Override void save(); @Override void copyTo(TrieStore target); @Override int trieSize(); @Override void setHash(int n, Keccak256 hash); byte[] serialize(); byte[] serializeTrie(); static Trie deserialize(byte[] bytes); @Override boolean hasStore(); static byte[] bytesToKey(byte[] bytes); Trie getSnapshotTo(Keccak256 hash); TrieStore getStore(); boolean hasLongValue(); byte[] getValueHash(); byte[] getValue();  }### Answer:
@Test public void bytesToKey() { Assert.assertArrayEquals(new byte[] { 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00 }, TrieImpl.bytesToKey(new byte[] { (byte)0xaa })); }