Breaking a 32-bit value into bytes for an ArrayList

Question

I am very new to Java and its collections and I'm trying to figure out "best" way to populate an ArrayList<Byte> in Java. In particular, I'm trying to take a 32 bit number, divide it into bytes, and put it into big-endian order into the list. I'm not particularly interested in hyper-optimizing in this case; I'd rather the code be clean and readable.

I've got a couple issues that are obvious to me, but the biggest one is that I hate the fact that I am initializing the list with bogus values before I update them. But my choices seem to be that, or adding the elements in ascending order, which seems to make the code to extract the bytes significantly more complex.

Am I missing a better solution?

public void Add32BitValue(int value) {
    // Adding 4 elements first to the list, so that 
    // I can modify them so they'll be in big endian
    // order.  
    // (The code to directly add them in big endian 
    // order seems much more complex.)
    for (int i=0; i<4; i++) {
        list.add((byte)0);
    }

    // Now that the elements are in the arraylist, they 
    // can be set.  
    for (int i = 3; i >= 0; i--) {
        list.set(list.size() + i - 4, (byte)value);
        value = value >> 8;
    }
}

Answer 1

Assuming your list was defined elsewhere, you could append the bytes of value as follows.

for(int i = 3; i >= 0; i--) {
    list.add((byte)((value >>> (i*8)) & 0xFF));
}

• It avoids pre-populating the arraylist
• It avoids resetting the byte already stored
• It avoids storing the shifted value back in value
• It uses a logical right shift to avoid sign extension of negative integers