Question

ByteBuffer byteBuffer is received over a TCP/IP connection, is visible in the NetBeans emulator, and contains 0x2b, 0x69, 0x80, and 0x3f in bytes 4, 5, 6, and 7 for this break.
If the endianess is wrong I would expect either an incorrect float value or possibly some type of numeric exception, but not always 0.0 for various sets of 4 bytes.
The same thing happens for a number of other floats read out of this ByteBuffer, at index 8, 12, etc. Why is the following always 0.0?

float f = byteBuffer.getFloat(4);

Answer 1

Unable to reproduce:

import java.nio.ByteBuffer;

public class Test {

    public static void main(String[] args) {
        byte[] bytes = { 0x1, 0x1, 0x1, 0x1,  0x2b, 0x69, (byte) 0x80, 0x3f };
        ByteBuffer buffer = ByteBuffer.wrap(bytes);
        System.out.println(buffer.getFloat(4));
    }
}

As aix commented, I suspect your buffer doesn’t really contain what you think it does.

What happens if you try it with getInt(4)?