Java: "Type mismatch: cannot convert from Byte[] to byte[]" [duplicate]

Question

I'm getting this odd error in my Java and I'm completely stuck.

private List<byte[]> sharedWorlds = Collections.synchronizedList(new ArrayList<byte[]>());

Byte[] y = sharedWorlds.toArray(new Byte[0]);

try{

    //this line won't compile!
    Utilities.writeByteArray(outStream, sharedWorlds.toArray(new Byte[0]));

}catch(Exception e){
    System.out.println("Error!");
}

Type mismatch: cannot convert from Byte[] to byte[]

The second parameter to "writeByteArray" needs to be a byte[] and not a Byte[]...

I could loop through a new byte[] and copy every element, but this seems unclean and inefficient?

I tried casting

(byte[]) sharedWorlds.toArray(new Byte[0])

but this errors with

Cannot cast from Byte[] to byte[]

My Java is rusty, but I have no idea what's going on here.

@GalAbra: It's not really a duplicate of that IMO, as byte is a primitive type... it's a slightly different situation. — Jon Skeet
– Jon Skeet, Commented Mar 3, 2018 at 11:28
What's unclear to me is why you're creating a Byte[] at all. Why not do everything using byte[]? — Jon Skeet
– Jon Skeet, Commented Mar 3, 2018 at 11:29
@Jon Skeet. I tried but I couldn't do it ;( the "sharedWorlds" object is of type List<byte[]> sharedWorlds — Eamorr
– Eamorr, Commented Mar 3, 2018 at 11:35
Then show what you've tried, using byte[] everywhere, and the error. — Jon Skeet
– Jon Skeet, Commented Mar 3, 2018 at 11:39

BateTech · Accepted Answer · 2018-03-03 11:44:05Z

0

It appears from some quick research that direct conversion isn't supported in Java.

You can use Apache Commons Lang ArrayUtils.toPrimitive() http://commons.apache.org/proper/commons-lang/javadocs/api-release/org/apache/commons/lang3/ArrayUtils.html#toPrimitive(java.lang.Integer[])

Or you can use a for loop to copy an object Byte array to a primitive byte array.

More info and example here Converting an array of objects to an array of their primitive types

edited Mar 3, 2018 at 11:44

answered Mar 3, 2018 at 11:37

BateTech

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3 Comments

Eamorr Over a year ago

From looking at @GalAbra's link, I ended up using Apache Commons Lang ArrayUtils i.e. Utilities.writeByteArray(outStream, ArrayUtils.toPrimitive(sharedWorlds.toArray(new Byte[0])));

user202729 Over a year ago

Why don't you just vote to close as duplicate?

BateTech Over a year ago

Good point, I will delete my answer and vote to close as duplicate

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