ByteBuffer buffer = ByteBuffer.allocate(64);
// This ArrayList contains all extracted Strings
ArrayList<String> complete = new ArrayList<String>();
// This is the test string
byte[] messages = "Hi\r\nHow are".getBytes("UTF-8");
buffer.put(messages);

buffer.flip();
int i;
for (i = 0; i < buffer.limit(); i++) {
    if (buffer.get(i) == '\n') {
        // Between 0 and i + 1 there is a complete message
        byte[] temp = new byte[i + 1];
        buffer.get(temp, 0, i + 1);
        complete.add(new String(temp, "UTF-8"));
        // Shift remaining bytes to 0
        buffer.compact();
        buffer.flip();
        // Start to look for another message
        i = 0;
    }
}
buffer.limit(64);
buffer.position(i);