4
I have:
byte mensagem[];
byte nonce[];
How do I concatenate the array nonce at the end of the array mensagem and store in a third array?
4 answers
4
This worked for me:
byte msg[];
byte nonce[];
byte[] mensagem = new byte[msg.length + nonce.length];
System.arraycopy(msg, 0, mensagem, 0, msg.length);
System.arraycopy(nonce, 0, mensagem, msg.length, nonce.length);
Source: https://stackoverflow.com/questions/5513152/easy-way-to-concatenate-two-byte-arrays
2
Try it like this:
byte [] terceiro = new byte[mensagem.length + nonce.length];
for (int i = 0; i < terceiro.length; i++) {
if (i < mensagem.length) {
terceiro[i] = mensagem[i];
} else {
terceiro[i] = nonce[i - mensagem.length];
}
}
2
One way to do this is to store them in one ByteArrayOutputStream:
byte[] primeiroArray = "stack".getBytes();
byte[] segundoArray = "overflow".getBytes();
ByteArrayOutputStream terceiroArray = new ByteArrayOutputStream();
terceiroArray.write(primeiroArray);
terceiroArray.write(segundoArray);
System.out.println(Arrays.toString(terceiroArray.toByteArray()));
System.out.println(terceiroArray.toString());
// [115, 116, 97, 99, 107, 111, 118, 101, 114, 102, 108, 111, 119]
// stackoverflow
Another possibility is to use the function ArrayUtils.addAll() library Apache Commons Lang:
byte[] terceiroArray = ArrayUtils.addAll(primeiroArray, segundoArray);
-
1
stack overflow. Nice example :)
2
byte [] terceiro = new byte[mensagem.length + nonce.length];
for (int i = 0; i < mensagem.length; i++) {
terceiro[i] = mensagem[i];
}
for (int i = mensagem.length; i < terceiro.length; i++) {
terceiro[i] = nonce[i - mensagem.length];
}
I declared the third array with capacity equal to the sum of the size of the previous two.
In the first loop I filled the third array with the bytes of the first array.
In the second loop I initialized an index for the third array at the position equal to the last index of the first array + 1. And from this index I started copying the items from the first array.
-
This solution at the end is the same as @Piovezan but uses a loop instead of IF; for those, like me, who don’t like Ifs very much :-)
-
All right, that makes it easier to understand. :)
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It worked, but I had to make some modifications. Can I edit your reply? You forgot to put the
+=for example.– Avelino
There is a bug in this code. When the int value is >9 (ie 10) it gives indexOutBoundsException. I believe he’s trying to put 2 bytes and it doesn’t fit.
– Avelino
@Avelino At his suggestion,
nonce[msg.length - i]will not be negative?– bfavaretto
So, the first solution of Piovezan did not work. I made some modifications, but only works until the 9, going from this gives error. Was it just the += that was wrong? (Gave indexOfBoundsException -1)
– Avelino
I tested the example and it looks ok. And it’s not necessary
+=because there is no string being concatenated, the code only works with arrays.– Piovezan