Java - Split array at first instance of value

Question

The method below receives byte[] b of indeterminate length. It contains a string of characters to be printed to a console-style window. I would like to split b at the first line-feed character, so that that character is included in the first array. However, at the moment this throws an ArrayOutOfBoundsError, because stringBytes and extraBytes are declared with zero size. How can I get around this problem?

byte[] stringBytes = {};
byte[] extraBytes = {};
int i = 0;

while(i < b.length) {
    stringBytes[i] = b[i];
    if(b[i] == '\n' && i + 1 != b.length) {
        while(i < b.length) {
            extraBytes[i - stringBytes.length] = b[i++];
        }

        break;
    }

    i++;
}

You could convert the whole byte[] to a String and split the string on \n. — assylias
– assylias, Commented Mar 29, 2013 at 16:35
You'll have to initialize extraBytes after you know how long it will be. — Louis Wasserman
– Louis Wasserman, Commented Mar 29, 2013 at 16:35
Either initialize your arrays like this: byte[] stringBytes = new byte[b.length] and shrink the arrays later on or use Lists and transform those to arrays afterwards. — skirsch
– skirsch, Commented Mar 29, 2013 at 16:37

Taylor · Accepted Answer · 2013-03-29 16:41:50Z

2

Try this:

byte[] stringBytes;
byte[] extraBytes;
int i = 0;

while(i < b.length) {
    if(b[i] == '\n' && i + 1 != b.length) {
        break;
    }

    i++;
}
stringBytes = java.util.Arrays.copyOf(b, i+1);
extraBytes = java.util.Arrays.copyOfRange(b, i+1, b.length - 1);

answered Mar 29, 2013 at 16:41

Taylor

4,0852 gold badges23 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Dan D. · Accepted Answer · 2013-03-29 16:36:05Z

1

I would rather build a String out of the bytes and use the String APIs.

However, if you really need to do the byte operations that you can declare stringBytes and extraBytes as List<Byte> such as you can add as many values as needed without knowing their size.

answered Mar 29, 2013 at 16:36

Dan D.

32.4k6 gold badges66 silver badges81 bronze badges

Comments

Joni · Accepted Answer · 2013-03-29 16:43:49Z

0

You can use a ByteArrayOutputStream as a light-weight expandable array of bytes:

To add a byte use the write method.
To get the bytes that you have written so far, use the toByteArray method.

For example:

ByteArrayOutputStream stringBytes = new ByteArrayOutputStream();
ByteArrayOutputStream extraBytes = new ByteArrayOutputStream();
int i = 0;

while(i < b.length) {
    stringBytes.write(b[i]);
    if(b[i] == '\n' && i + 1 != b.length) {
        i++;
        extraBytes.write(b, i, stringBytes.length - i);
        break;
    }
    i++;
}

edited Mar 29, 2013 at 16:43

answered Mar 29, 2013 at 16:38

Joni

112k14 gold badges151 silver badges201 bronze badges

Collectives™ on Stack Overflow

Java - Split array at first instance of value

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related