java基本类型与字节数据之间的转换

public class PrimitiveTypeConverter {

	public PrimitiveTypeConverter() {

	}

	/**
	 * 获取字节数组的整型值
	 * 
	 * @param bs
	 * @return
	 */
	public static int bytesToInt(byte[] bs) {
		int intValue = 0;

		for (int i = 0; i < 4; i++) {
			intValue += (bs[i] & 0xFF) << (8 * i); // 需要反转时是(8*(3-i))
		}

		return intValue;
	}

	/**
	 * 获取字节数组的整型值
	 * 
	 * @param bs
	 * @return
	 */
	public static int bytesToIntForReverse(byte[] bs) {
		int intValue = 0;

		for (int i = 0; i < 4; i++) {
			intValue += (bs[i] & 0xFF) << (8 * (3 - i)); // 需要反转时是(8*(3-i))
		}

		return intValue;
	}

	/**
	 * 获取字节数组的整型值
	 * 
	 * @param bs
	 * @param startIndex
	 * @return
	 */
	public static int bytesToInt(byte[] bs, int startIndex) {
		int intValue = 0;

		for (int i = 0; i < 4; i++) {
			intValue += (bs[i + startIndex] & 0xFF) << (8 * i); // 需要反转时是(8*(3-i))
		}

		return intValue;
	}

	/**
	 * 获取字节数组的整型值
	 * 
	 * @param bs
	 * @param startIndex
	 * @return
	 */
	public static int bytesToIntForReserve(byte[] bs, int startIndex) {
		int intValue = 0;

		for (int i = 0; i < 4; i++) {
			intValue += (bs[i + startIndex] & 0xFF) << (8 * (3 - i)); // 需要反转时是(8*(3-i))
		}

		return intValue;
	}

	/**
	 * 获取字节数组的长整型值
	 * 
	 * @param bs
	 * @return
	 */
	public static long bytesToLong(byte[] bs) {
		long longValue = 0L;
		for (int i = 0; i < 8; i++) {
			longValue += (long) ((bs[i] & 0xFF) << (8 * i)); // 或者(8*(7-i))
			// System.out.println(longValue);
		}

		return longValue;
	}

	/**
	 * 获取字节数组的长整型值
	 * 
	 * @param bs
	 * @param startIndex
	 *            字节数组的起始位置
	 * @return
	 */
	public static long bytesToLong(byte[] bs, int startIndex) {
		long longValue = 0L;
		for (int i = 0; i < 8; i++) {
			longValue += (bs[i + startIndex] & 0xFF) << (8 * i); // 或者(8*(7-i))
		}

		return longValue;
	}

	/**
	 * 获取网络字节数组的长整型值，需反转
	 * 
	 * @param bs
	 * @param startIndex
	 *            字节数组的起始位置
	 * @return
	 */
	public static long bytesToLongForReverse(byte[] bs, int startIndex) {
		long longValue = 0L;
		for (int i = 0; i < 8; i++) {
			longValue += (long) (bs[i + startIndex] & 0xFF) << (8 * (7 - i)); // 或者(8*(7-i))
		}

		return longValue;
	}

	/**
	 * 整型转换成字节数组
	 * 
	 * @param num
	 * @return
	 */
	public static byte[] intToBytes(int num) {
		byte[] b = new byte[4];
		for (int i = 0; i < 4; i++) {
			b[i] = (byte) (num >>> (24 - i * 8));
		}
		return b;
	}

	/**
	 * 长整型转换成字节数组
	 * 
	 * @param num
	 * @return
	 */
	public static byte[] longToBytes(long num) {
		byte[] b = new byte[8];
		for (int i = 0; i < 8; i++) {
			b[i] = (byte) (num >>> (i * 8));
			// System.out.println(b[i]);
		}
		return b;
	}

	public static int bytesToIntEx(byte b[]) {
		if (b != null && b.length > 0) {
			if (b.length >= 4) {
				return b[3] & 0xff | (b[2] & 0xff) << 8 | (b[1] & 0xff) << 16
						| (b[0] & 0xff) << 24;
			} else if (b.length == 2) {
				return bytes2ToInt(b);
			} else {
				return 0;
			}

		} else {
			return 0;
		}

	}

	public static int bytes2ToInt(byte b[]) {
		return b[1] & 0xff | (b[0] & 0xff) << 8;
	}

	public static int byteToInt(byte b) {
		return (int) b;
	}

	public static int byteToUnsignedInt(byte b) {
		return b & 0xff;
	}

}