I have a class in which I am passing certain parameters through the constructor and then using those parameters to make one final byte array with a proper format (header + data):public final class Frame {  private final byte addressedCenter;  private final byte version;  private final Map<byte[], byte[]> keyDataHolder;  private final long location;  private final long locationFrom;  private final long locationOrigin;  private final byte partition;  private final byte copy;  public Frame(byte addressedCenter, byte version,      Map<byte[], byte[]> keyDataHolder, long location, long locationFrom,      long locationOrigin, byte partition, byte copy) {    this.addressedCenter = addressedCenter;    this.version = version;    this.keyDataHolder = keyDataHolder;    this.location = location;    this.locationFrom = locationFrom;    this.locationOrigin = locationOrigin;    this.partition = partition;    this.copy = copy;  }  public byte[] serialize() {    // All of the data is embedded in a binary array with fixed maximum size 70000    ByteBuffer byteBuffer = ByteBuffer.allocate(70000);    byteBuffer.order(ByteOrder.BIG_ENDIAN);    int numOfRecords = keyDataHolder.size();    int bufferUsed = getBufferUsed(keyDataHolder); // 36 + dataSize + 1 + 1 + keyLength + 8 + 2;    // header layout    byteBuffer.put(addressedCenter); // byte    byteBuffer.put(version); // byte    byteBuffer.putInt(numOfRecords); // int    byteBuffer.putInt(bufferUsed); // int    byteBuffer.putLong(location); // long    byteBuffer.putLong(locationFrom); // long    byteBuffer.putLong(locationOrigin); // long    byteBuffer.put(partition); // byte    byteBuffer.put(copy); // byte    // now the data layout    for (Map.Entry<byte[], byte[]> entry : keyDataHolder.entrySet()) {      byte keyType = 0;      byte keyLength = (byte) entry.getKey().length;      byte[] key = entry.getKey();      byte[] data = entry.getValue();      short dataSize = (short) data.length;      ByteBuffer dataBuffer = ByteBuffer.wrap(data);      long timestamp = 0;      if (dataSize > 10) {        timestamp = dataBuffer.getLong(2);                    }             byteBuffer.put(keyType);      byteBuffer.put(keyLength);      byteBuffer.put(key);      byteBuffer.putLong(timestamp);      byteBuffer.putShort(dataSize);      byteBuffer.put(data);    }    return byteBuffer.array();  }  private int getBufferUsed(final Map<byte[], byte[]> keyDataHolder) {    int size = 36;    for (Map.Entry<byte[], byte[]> entry : keyDataHolder.entrySet()) {      size += 1 + 1 + 8 + 2;      size += entry.getKey().length;      size += entry.getValue().length;    }    return size;  }  }I would like to know if it can be improved in any way. As you can see right now, I am allocating ByteBuffer with predefined size of 70000. Is there a better way by which I can allocate the size I am using while making ByteBuffer instead of using a hardcoded 70000?
Serialize data into one byte array using ByteBuffer
java;array;serialization
A minor aesthetics adviceYou can save some typing by using the method chains over ByteBuffer:private int getBufferCapacity(final Map<byte[], byte[]> keyDataHolder) {    int size = 36;    for (Map.Entry<byte[], byte[]> entry : keyDataHolder.entrySet()) {        size += 1 + 1 + 8 + 2;        size += entry.getKey().length;        size += entry.getValue().length;    }    return size;}public byte[] serialize2() {    ByteBuffer byteBuffer = ByteBuffer.allocate(getBufferCapacity(keyDataHolder))            .order(ByteOrder.BIG_ENDIAN);    // Use chaining:    byteBuffer.put(addressedCenter)            .put(version)            .putInt(keyDataHolder.size())            .putInt(getBufferUsed(keyDataHolder))            .putLong(location)            .putLong(locationFrom)            .putLong(locationOrigin)            .put(partition)            .put(copy);    for (Map.Entry<byte[], byte[]> entry : keyDataHolder.entrySet()) {        byte keyType = 0;        byte[] key = entry.getKey();        byte[] value = entry.getValue(); // A map mapping is often called a        // key/value -pair.        byte keyLength = (byte) key.length;        short valueLength = (short) value.length;        ByteBuffer dataBuffer = ByteBuffer.wrap(value);        // Short cut:        long timestamp = valueLength > 10 ? dataBuffer.getLong(2) : 0;        // Chaining:        byteBuffer.put(keyType)                .put(keyLength)                .put(key)                .putLong(timestamp)                .putShort(valueLength)                .put(value);    }    return byteBuffer.array();}Also, when you deal with maps, the conventional terminology for a mapping is a key/value-pair. For this reason, I would rewritebyte[] key = entry.getKey();byte[] data = entry.getValue();tobyte[] key = entry.getKey();byte[] value = entry.getValue();Then, later on in the code, I would changebyte keyLength = (byte) entry.getKey().length;withbyte keyLength = key.length;Instead oflong timestamp = 0;if (dataSize > 10) {    timestamp = dataBuffer.getLong(2);              }   you can write an one-liner:long timestamp = valueLength > 10 ? dataBuffer.getLong(2) : 0;Finally, since you know your file format, you should be able to come up with a function that computes the exact size of the file for particular set of data; call it foo. Now, you would normally do:ByteBuffer byteBuffer = ByteBuffer.allocate(foo(keyDataHolder));Hope that helps.