How to pass a List of byte[] as a varargs parameter?

Question

My question is very close to this question. But it's not the same. I have a method that accepts varargs with a signature like

static void doSomething(byte[]... values)

And a List of byte[] that I want to send to that method.

List<byte[]> myList;

How do I convert myList to byte[] varargs to send to doSomething?

I thought it would be something like

doSomething(myList.toArray(new Byte[][0]));

but that did not work - It says unexpected token at 0])).

Thanks in advance.

Answer 1

There are two problems here:

• Byte and byte are different types
• The syntax for creating the array-of-arrays is incorrect - it should be new byte[0][]. Arrays of arrays are annoying in that respect, to be honest. I can certainly understand why you'd expect to put the [0] at the end, but in this case it's just not that way...

With that change in place, it's fine:

import java.util.*;

public class Test {

    public static void main(String[] args) {
        List<byte[]> myList = new ArrayList<>();
        myList.add(new byte[10]);
        myList.add(new byte[5]);
        doSomething(myList.toArray(new byte[0][]));
    }

    static void doSomething(byte[]... values) {
        System.out.printf("Array contained %d values%n", values.length);
    }
}