Java byte array invert the word endian for length of 4 bytes

/**//from  w w  w . jav a2s .  c o m
 * ByteUtilities.java - Byte manipulation functions.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 * @since MINA 2.0.0-M3
 */
public class Main {


    /**
     * Invert the endianness of words (4 bytes) in the given byte array
     * starting at the given offset and repeating length/4 times.
     * eg: b0b1b2b3 -> b3b2b1b0
     *
     * @param b the byte array
     * @param offset the offset at which to change word start
     * @param length the number of bytes on which to operate
     * (should be a multiple of 4)
     */
    public final static void changeWordEndianess(byte[] b, int offset,
            int length) {
        byte tmp;

        for (int i = offset; i < offset + length; i += 4) {
            tmp = b[i];
            b[i] = b[i + 3];
            b[i + 3] = tmp;
            tmp = b[i + 1];
            b[i + 1] = b[i + 2];
            b[i + 2] = tmp;
        }
    }

    /**
     * Invert two bytes in the given byte array starting at the given
     * offset and repeating the inversion length/2 times.
     * eg: b0b1 -> b1b0
     *
     * @param b the byte array
     * @param offset the offset at which to change word start
     * @param length the number of bytes on which to operate
     * (should be a multiple of 2)
     */
    public final static void changeByteEndianess(byte[] b, int offset,
            int length) {
        byte tmp;

        for (int i = offset; i < offset + length; i += 2) {
            tmp = b[i];
            b[i] = b[i + 1];
            b[i + 1] = tmp;
        }
    }
}
/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */