Question

I have a byte array in Java of size 4, which I am trying to put the first two bytes of into ByteBuffer.

Here is how I am doing it:

byte[] array = new byte[4];
ByteBuffer buff = ByteBuffer.allocate(2);
buff.put(array, 0, 2);

What’s wrong with my code?

EDIT:

byte[] currRecord = new byte[4];
byte[] leftRecord = new byte[4];
// Code that populates the records
ByteBuffer currKey = ByteBuffer.allocate(2);
currKey = currKey.put(currRecord, 0, 2);
ByteBuffer leftKey = ByteBuffer.allocate(2);
leftKey = leftKey.put(leftRecord, 0, 2);

Then I am trying to compare both ByteBuffers as follows:

if (currKey.compareTo(leftKey) >= 0)
    return;

My comparison is always wrong. When debugging, I am pretty sure currRecord and leftRecord have the right values. The ByteBuffers also have the right values (according to the debugger). What is the problem here?

Answer 1

The compareTo compares the remaining bytes of the buffers. Therefore you must first flip() both buffers before the comparison.

Without the flip you will compare the bytes[2..3] in each buffer. Because you did not write those bytes, they all will be zero. With the flip you will compare the bytes[0..1] which contains the data you have written from the arrays.