Converting all objects in arraylist to byte array in java

Question

I have an ArrayList with data that is my own custom object and I need to convert all of them into a byte array. I am able to convert the object to a byte array by serializing it but I need all the objects to be serialized into one array.

ArrayList<MyObject> myArrayList = new ArrayList<MyObject>();
// Getting a list of objects of database (any unknown number)
for(int counter = 0; counter < myObj.size(); counter++) {
    byte[] myData = serialize(myObj.get(counter));
}

Now how do I go about doing this for multiple objects as I do not know the length to initialize by byte array buffer?

Couldn't you just serialize the arraylist itself?

Cruncher
– Cruncher

2015-03-11 22:13:49 +00:00
Commented Mar 11, 2015 at 22:13 — Cruncher
– Cruncher, Commented Mar 11, 2015 at 22:13

manf · Accepted Answer · 2015-03-11 22:21:20Z

1

If you really wish to convert it into a single byte[] juste use the ByteArrayOutputStream and call the appropriate functions as you need them.

Although you also need to consider turning this byte[] into a proper List again.

answered Mar 11, 2015 at 22:21

manf

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2 Comments

JourneyWithAndroid Over a year ago

I need just the byte array as I need to send that data to a ble device.

manf Over a year ago

The given class can even write to a given output Stream directly, making it integrate smoothly - or you could write the data to the output stream directly without the need to make them a single byte array at all.

Destroyica · Accepted Answer · 2015-03-11 22:29:56Z

0

Preallocate an array

byte[][] data = new byte[myObj.size()][];
long size = 0;

Generate bytes

for(int counter = 0; counter < myObj.size(); counter++) {
    data[counter] = serialize(myObj.get(counter));
    size += data[counter].length;
}

Concat to a final buffer "allData":

byte[] allData = new byte[size];
long curs = 0;
for(int i = 0; i < data.length; i++) {
    int length = data[i].length;
    System.arraycopy(data[i], 0, allData, curs, length);
    curs += length;
}

answered Mar 11, 2015 at 22:29

Destroyica

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