Java ByteBuffer convert to hexadecimal string

/*//from   w  w w. j  a va 2 s  . c om
Copyright (c) 2005 Health Market Science, Inc.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
USA

You can contact Health Market Science at info@healthmarketscience.com
or at the following address:

Health Market Science
2700 Horizon Drive
Suite 200
King of Prussia, PA 19406
 */
import java.nio.ByteBuffer;

public class Main {
  public static void main(String[] argv) throws Exception {
    byte[] array = new byte[] { 34, 35, 36, 37, 37, 37, 67, 68, 69 };
    ByteBuffer bb = ByteBuffer.wrap(array);
    System.out.println(toHexString(bb,bb.limit()));
  }

  private static final String[] HEX_CHARS = new String[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B",
      "C", "D", "E", "F" };
  private static final int NUM_BYTES_PER_BLOCK = 4;
  private static final int NUM_BYTES_PER_LINE = 24;

  /**
   * Convert a byte buffer to a hexadecimal string for display
   * 
   * @param buffer
   *          Buffer to display, starting at offset 0
   * @param size
   *          Number of bytes to read from the buffer
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer, int size) {
    return toHexString(buffer, 0, size);
  }

  /**
   * Convert a byte array to a hexadecimal string for display
   * 
   * @param array
   *          byte array to display, starting at offset 0
   * @return The display String
   */
  public static String toHexString(byte[] array) {
    return toHexString(ByteBuffer.wrap(array), 0, array.length);
  }

  /**
   * Convert a byte buffer to a hexadecimal string for display
   * 
   * @param buffer
   *          Buffer to display, starting at offset 0
   * @param offset
   *          Offset at which to start reading the buffer
   * @param size
   *          Number of bytes to read from the buffer
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer, int offset, int size) {
    return toHexString(buffer, offset, size, true);
  }

  /**
   * Convert a byte buffer to a hexadecimal string for display
   * 
   * @param buffer
   *          Buffer to display, starting at offset 0
   * @param offset
   *          Offset at which to start reading the buffer
   * @param size
   *          Number of bytes to read from the buffer
   * @param formatted
   *          flag indicating if formatting is required
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer, int offset, int size, boolean formatted) {

    StringBuilder rtn = new StringBuilder();
    int position = buffer.position();
    buffer.position(offset);

    for (int i = 0; i < size; i++) {
      byte b = buffer.get();
      byte h = (byte) (b & 0xF0);
      h = (byte) (h >>> 4);
      h = (byte) (h & 0x0F);
      rtn.append(HEX_CHARS[h]);
      h = (byte) (b & 0x0F);
      rtn.append(HEX_CHARS[h]);

      int next = (i + 1);
      if (formatted && (next < size)) {
        if ((next % NUM_BYTES_PER_LINE) == 0) {

          rtn.append("\n");

        } else {

          rtn.append(" ");

          if ((next % NUM_BYTES_PER_BLOCK) == 0) {
            rtn.append(" ");
          }
        }
      }
    }

    buffer.position(position);
    return rtn.toString();
  }

}