Cannot cast from Byte to byte[] java

Question

I am trying to convert byte array into image in android. I have a ArrayList<Byte> arrays; that contains all byte arrays that I want to convert. Now at

byt = (byte[]) arrays.get(0); 

its giving me Cannot cast from Byte to byte[] java exception.

        byte[] byt;
        byt = new byte[4096];
        byt = (byte[]) arrays.get(0) ;
        BufferedImage bImageFromConvert = null;
        InputStream in = new ByteArrayInputStream(byt);

        try {
            bImageFromConvert = ImageIO.read(in);
            SaveImages();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

How can I solve this?

Answer 1

The ArrayList doesn't contain Byte[] or byte[] values, however the list itself can be converted to a byte array as it contains individual byte values

        byte[] bytes = new byte[array.size()];
        for (int i = 0; i < array.size(); i++) {
            bytes[i] = array.get(i);
        }

Answer 2

Try using ByteArrayOutputStream instead of an arraylist, its better. Then you use ByteArrayOutputStream.toByteArray().

Answer 3

ArrayList<Byte> arrays; does not contain a list of `Byte[]'. It is a single list of boxed Byte objects.

You will need to do a conversion by hand:

 byte[] byteArray = new byte[arrays.size()];

 for (int i=0;i<byteArray.length;i++) {
    byteArray[i] = arrays.get(i);
 }

The loop will unbox the Byte to a byte for you as it is placed into the array.

Answer 4

You seem to be misusing the ImageIO API (correct me if I misunderstood):

You can use ImageIO.read with 3 different inputs:

• URL
• File
• InputStream

If you have a file to load - just pass it like so:

bImageFromConvert = ImageIO.read(new File("someFile.jpg"));

Or like this if it is within your application:

bImageFromConvert =
   ImageIO.read(this.getClass().getClassloader().getResourceAsStream("com/myapp/images/someFile.jpg"));

If you are getting the data as bytes from an outside source - try using a byte[] instead of List<Byte> which I assume you are using as it is more fitting to the problem you are trying to solve.

Also, note that you allocated only 4K for the image - and this might not be enough for loading your image - which (should) cause ImageIO.read to fail.

I'm not adding anything about using a URL - but I assume it is obvious.

If this does not answer your question please add more relevant inputs.

Answer 5

As I understand you are trying to get an image from soap service to your android device.

I suggest to use the following method,

Read the SOAP object property as a String.

String mPhoto;

 if (soapObject.hasProperty(PHOTO)) {
        Object obj = soapObject.getProperty(PHOTO);
        if (obj != null && obj.getClass().equals(SoapPrimitive.class)) {
            SoapPrimitive j = (SoapPrimitive) obj;
            mPhoto = j.toString();
        } else if (obj != null && obj instanceof String) {
            mPhoto = obj.toString();
        } else {
            mPhoto = null;
        }
    }

Then convert that String to byte[]

public byte[] getPhoto() {
    if (mPhoto != null) {
           // org.kobjects.base64.Base64;
        return Base64.decode(mPhoto);
    } else {
        return null;
    }
}

Decoding is important to reconstruct the same byte[] sent from the service.

Answer 6

If you couldn't use another solution with Byte[] instead. Then you could use toPrimitive method from ArrayUtils class from Apache Lang library. Or use this bellow code:

public static byte[] toPrimitive(final Byte[] array) {
        if (array == null) {
            return null;
        } else if (array.length == 0) {
            return EMPTY_BYTE_ARRAY;
        }
        final byte[] result = new byte[array.length];
        for (int i = 0; i < array.length; i++) {
            result[i] = array[i].byteValue();
        }
        return result;
    }

Answer 7

You have to declare your ArrayList<Byte> as ArrayList<byte[]> arrays;.

Your current declaration, as it is, does not store a list of byte arrays, but a list of Byte objects, not arrays. Even if your arrays were declared as ArrayList<Byte[]> arrays;, you cannot cast a Byte[] array to a byte[] array. Java does not support directly casting primitive data types and their wrapper types, nor their array types.

Primitives and their wrapper types are boxed or un-boxed. The compiler silently replaces declarations such as Integer myInt = 0; with Integer myInt = Integer.valueOf(0);, and int myInt = myWrappedInt; with int myInt = myWrappedInt.intValue(); because of the auto-(un)boxing feature introduced in Java 5.

Answer 8

You can use the ArrayList.toArray(T[]) method, like so:

Byte[] byteArray = new Byte[arrays.size()];
ArrayList.toArray(byteArray);

This method uses System.arrayCopy, a native method. It is a lot faster than iterating through your whole ArrayList.

Answer 9

The error occurs on line 3

        byt = (byte[]) arrays.get(0) ;

arrays.get(0) returns a Byte which you then try to cast to a byte[]

Answer 10

If you tried to put byte-arrays into the ArrayList arrays, then you should correct its declaration to:

ArrayList<Byte[]> arrays = new ArrayList<Byte[]>();

and fill it with your data.