【工具类】Java常用数据类型的转换

/**
 * @declaration 常用数据类型转换 
 * @date 2012-10-30 下午2:44:25 
 *
 */
public class DataTypeChangeHelper {
	/**
	 * 将一个单字节的byte转换成32位的int
	 * 
	 * @param b
	 *            byte
	 * @return convert result
	 */
	public static int unsignedByteToInt(byte b) {
		return b & 0xFF;
	}

	/**
	 * 将一个单字节的Byte转换成十六进制的数
	 * 
	 * @param b
	 *            byte
	 * @return convert result
	 */
	public static String byteToHex(byte b) {
		int i = b & 0xFF;
		return Integer.toHexString(i);
	}

	/**
	 * 将一个4byte的数组转换成32位的int
	 * 
	 * @param buf
	 *            bytes buffer
	 * @param byte[]中开始转换的位置
	 * @return convert result
	 */
	public static long unsigned4BytesToInt(byte[] buf, int pos) {
		int firstByte = 0;
		int secondByte = 0;
		int thirdByte = 0;
		int fourthByte = 0;
		int index = pos;
		firstByte = (0x000000FF & (buf[index]));
		secondByte = (0x000000FF & (buf[index + 1]));
		thirdByte = (0x000000FF & (buf[index + 2]));
		fourthByte = (0x000000FF & (buf[index + 3]));
		index = index + 4;
		return (firstByte << 24 | secondByte << 16 | thirdByte << 8 | fourthByte) & 0xFFFFFFFFL;
	}
	
	/**
	 * 将一个byte的数组转换成short数组
	 * @param buf 数据
	 * @param size 数据大小
	 * @return
	 */
	public short[] byteAryToShortAry(byte [] buf, int size){
		int arySize = size / 2;
		short [] result = new short[arySize];
		
		int firstByte = 0;
		int secondByte = 0;
		for (int i = 0; i < arySize; i+=2){
			firstByte = (0x000000FF & (buf[i]));
			secondByte = (0x000000FF & (buf[i + 1]));
			result[i] = (short)((firstByte << 8 | secondByte) & 0xffff);
		}
		return result;
	}
	
	/**
	 * 将一个short的数组转换成byte数组
	 * @param buf
	 * @param size
	 * @return
	 */
	public byte[] shortAryToByteAry(short [] buf, int size){
		int arySize = size * 2;
		byte [] result = new byte[arySize];
		
		for (int i = 0; i < arySize; i+=2){
			result[i] = (byte)(0xFF & (buf[i/2]>>8));
			result[i+1] = (byte)(0xFF & (buf[i/2]));
			
		}
		return result;
	}

	/**
	 * 将16位的short转换成byte数组
	 * 
	 * @param s
	 *            short
	 * @return byte[] 长度为2
	 * */
	public static byte[] shortToByteArray(short s) {
		byte[] targets = new byte[2];
		for (int i = 0; i < 2; i++) {
			int offset = (targets.length - 1 - i) * 8;
			targets[i] = (byte) ((s >>> offset) & 0xff);
		}
		return targets;
	}

	/**
	 * 将32位整数转换成长度为4的byte数组
	 * 
	 * @param s
	 *            int
	 * @return byte[]
	 * */
	public static byte[] intToByteArray(int s) {
		byte[] targets = new byte[2];
		for (int i = 0; i < 4; i++) {
			int offset = (targets.length - 1 - i) * 8;
			targets[i] = (byte) ((s >>> offset) & 0xff);
		}
		return targets;
	}

	/**
	 * long to byte[]
	 * 
	 * @param s
	 *            long
	 * @return byte[]
	 * */
	public static byte[] longToByteArray(long s) {
		byte[] targets = new byte[2];
		for (int i = 0; i < 8; i++) {
			int offset = (targets.length - 1 - i) * 8;
			targets[i] = (byte) ((s >>> offset) & 0xff);
		}
		return targets;
	}

	/**32位int转byte[]*/
	public static byte[] int2byte(int res) {
		byte[] targets = new byte[4];
		targets[0] = (byte) (res & 0xff);// 最低位
		targets[1] = (byte) ((res >> 8) & 0xff);// 次低位
		targets[2] = (byte) ((res >> 16) & 0xff);// 次高位
		targets[3] = (byte) (res >>> 24);// 最高位,无符号右移。
		return targets;
	}

	/**
	 * 将长度为2的byte数组转换为16位int
	 * 
	 * @param res
	 *            byte[]
	 * @return int
	 * */
	public static int byte2int(byte[] res) {
		// res = InversionByte(res);
		// 一个byte数据左移24位变成0x??000000，再右移8位变成0x00??0000
		int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00); // | 表示安位或
		return targets;
	}
}