How to use System.arraycopy in for loop

Question

I have ArrayList of bytes.I want to use System.arraycopy function for combile all bytes of the ArrayList.Following is my code.

public void createFile(ArrayList<byte[]> arrayList) throws IOException
{
    FileOutputStream fos = new FileOutputStream(Constant.MERGE_DIRECOTRY + "out" + Constant.FILE_EXTENSION.toString());
    for(byte[] data: arrayList)
        fos.write(data);

    fos.close();
    MediaPlayer mp = MediaPlayer.create(MergerActivity.this, Uri.parse(Constant.MERGE_DIRECOTRY + "out" + Constant.FILE_EXTENSION.toString()));
    if(mp != null)
    {
        totalduration = totalduration + mp.getDuration();
        Log.d("duration",""+Utilis.milliSecondsToTimer(totalduration));
    }
}

How can i use System.arraycopy function instead if fos.write().

Where should that copy too? Please give an example.

greenapps
– greenapps

2017-11-22 06:30:25 +00:00
Commented Nov 22, 2017 at 6:30 — greenapps
– greenapps, Commented Nov 22, 2017 at 6:30

Eran · Accepted Answer · 2017-11-22 06:30:08Z

2

In order to use System.arraycopy you have to first find out the required length of the output array:

int len = 0;
for(byte[] data: arrayList)
    len += data.length;

Now you can copy the source arrays to a target array:

byte[] output = new byte[len];
int pos = 0;
for(byte[] data: arrayList) {
    System.arrayscopy(data,0,output,pos,data.length);
    pos+=data.length;
}

answered Nov 22, 2017 at 6:30

Eran

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