Java中數值類型與字節數組之間的轉換大法(精簡)

/**
 * 整型轉字節數組
 *
 * @param data       待轉換數值
 * @param bytes      轉換后的數組
 * @param beginIndex 數組起始下標
 * @return
 */
public static int int2Bytes(int data, byte[] bytes, int beginIndex) {
    if (null == bytes || beginIndex < 0 || bytes.length < beginIndex + 4) {
        return -1;
    }

    try {
        bytes[beginIndex++] = (byte) (data & 0xff);
        bytes[beginIndex++] = (byte) (data >> 8 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 16 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 24 & 0xff);
    } catch (RuntimeException e) {
        throw e;
    }

    return beginIndex;
}

/**
 * 長整型轉字節數組
 *
 * @param data       待轉換數值
 * @param bytes      轉換后的數組
 * @param beginIndex 數組起始下標
 * @return
 */
public static int long2Bytes(long data, byte[] bytes, int beginIndex) {
    if (null == bytes || beginIndex < 0 || bytes.length < beginIndex + 8) {
        return -1;
    }

    try {
        bytes[beginIndex++] = (byte) (data & 0xff);
        bytes[beginIndex++] = (byte) (data >> 8 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 16 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 24 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 32 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 40 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 48 & 0xff);
        bytes[beginIndex++] = (byte) (data >> 56 & 0xff);
    } catch (RuntimeException e) {
        throw e;
    }

    return beginIndex;
}

/**
 * 字節數組轉整型
 *
 * @param bytes      待轉換數組
 * @param beginIndex 數組起始下標
 * @return
 */
public static int bytes2Int(byte[] bytes, int beginIndex) {
    if (null == bytes || beginIndex < 0 || bytes.length < beginIndex + 4) {
        return -1;
    }

    int result = 0;
    try {
        int tmpVal = 0;
        for (int i = 0; i < 4; i++) {
            tmpVal = (bytes[i + beginIndex] << (i * 8));
            switch (i) {
                case 0:
                    tmpVal = tmpVal & 0x000000FF;
                    break;
                case 1:
                    tmpVal = tmpVal & 0x0000FF00;
                    break;
                case 2:
                    tmpVal = tmpVal & 0x00FF0000;
                    break;
                case 3:
                    tmpVal = tmpVal & 0xFF000000;
                    break;
            }

            result |= tmpVal;
        }
    } catch (RuntimeException e) {
        throw e;
    }

    return result;
}

/**
 * 字節數組轉長整型
 *
 * @param bytes      待轉換數組
 * @param beginIndex 數組起始下標
 * @return
 */
public static long bytes2Long(byte[] bytes, int beginIndex) {
    if (null == bytes || beginIndex < 0 || bytes.length < beginIndex + 8) {
        return -1L;
    }

    long result = 0L;
    try {
        int shift = 0;
        for (int i = 0; i < 8; i++) {
            shift = i << 3;
            result |= ((long) 0xff << shift) & ((long) bytes[i + beginIndex] << shift);
        }
    } catch (RuntimeException e) {
        throw e;
    }

    return result;
}