Simple hex dumping handler that mimicks wireshark for network based communication

HexDumpHandler.java

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandler;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelPipeline; 
import java.nio.charset.Charset; 
import java.util.Arrays; 

public class HexDumpHandler extends ChannelInboundHandlerAdapter {

    private static final int columnCount = 8;
    private static final int groupCount = 32;
    private static final Charset CHARSET = Charset.forName("UTF-8");

    /**
     * Calls {@link ChannelHandlerContext#fireChannelRead(Object)} to forward
     * to the next {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
     * <p>
     * Sub-classes may override this method to change behavior.
     *
     * @param ctx
     * @param msg
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        //super.channelRead(ctx, msg);
        final ByteBuf buffer = ((ByteBuf) msg);
        int readableBytes = buffer.readableBytes();
        byte[] data = new byte[readableBytes];
        buffer.readBytes(data);
        //int requiredPadding = groupCount - (readableBytes % groupCount);
        for (int i = 0; i < readableBytes / groupCount + 1; i++) {
            int maxlen = Math.min((i + 1) * groupCount, data.length);
            byte[] column = Arrays.copyOfRange(data, i * groupCount, maxlen);
            int originalLength = column.length;
            column = Arrays.copyOf(column, groupCount);
            Arrays.fill(column, originalLength, groupCount, (byte) 0x20);
            for (int j = 0; j < column.length; j++) {
                if(j > 0 && j % columnCount == 0)
                    System.out.print(" ");
                System.out.print(String.format("%02x", column[j]));
            }
            System.out.print("\t");
            System.out.println(new String(column, CHARSET)
                    .replaceAll("\r", " ")
                    .replaceAll("\n", " ")
                    .replaceAll(" ", "."));
        }
        System.out.println("- END -");
        buffer.resetReaderIndex();
        super.channelRead(ctx, msg);
        //String data = buffer.getCharSequence(0, readableBytes, CHARSET).toString().replaceAll("\n", " 0x0A" + LINE_SEPARATOR);
        //System.out.print(data);
        //System.out.print("- END -");
    }
}