【转】java byte转long、double、float、int、short，或者long、double、float、int、short转byte

原文网址：http://www.xuebuyuan.com/988752.html

java byte与其他数据类型的转换主要用于二进制数据的编码和解码，主要用于网络传输，读写二进制文件，java和c++服务器之间的数据通信等等

以下是总结的源码

/**
* BYTE转INT
*
* @param b
* @return
*/
protected int byteArrayToInt(byte[] b) {
return (b[0] << 24) + ((b[1] & 0xFF) << 16) + ((b[2] & 0xFF) << 8)
+ (b[3] & 0xFF);
}
/**
* BYTE转SHORT
*
* @param b
* @return
*/
protected int byteArrayToShort(byte[] b) {
return (b[0] << 8) + (b[1] & 0xFF);
}

/**
* SHORT转BYTE数据
*
* @param s
* @return
*/
protected byte[] shortToByteArray(short s) {
byte[] shortBuf = new byte[2];
for (int i = 0; i < 2; i++) {
int offset = (shortBuf.length - 1 - i) * 8;
shortBuf[i] = (byte) ((s >>> offset) & 0xff);
}
return shortBuf;
}

/**
* INT数据转BYTE数据
*
* @param i
* @return
*/
protected byte[] intToByteArray(int i) {
byte[] result = new byte[4];
result[0] = (byte) ((i >> 24) & 0xFF);
result[1] = (byte) ((i >> 16) & 0xFF);
result[2] = (byte) ((i >> 8) & 0xFF);
result[3] = (byte) (i & 0xFF);
return result;
}

/**
* 转换long型为byte数组
*
* @param bb
* @param x
* @param index
*/
public byte[] longToByteArray(long x, int index) {
byte[] bb = new byte[8];
bb[index + 7] = (byte) (x >> 56);
bb[index + 6] = (byte) (x >> 48);
bb[index + 5] = (byte) (x >> 40);
bb[index + 4] = (byte) (x >> 32);
bb[index + 3] = (byte) (x >> 24);
bb[index + 2] = (byte) (x >> 16);
bb[index + 1] = (byte) (x >> 8);
bb[index + 0] = (byte) (x >> 0);
return bb;
}

/**
* 通过byte数组取到long
*
* @param bb
* @param index
* @return
*/
public long byteArrayToLong(byte[] bb, int index) {
return ((((long) bb[index + 7] & 0xff) << 56)
| (((long) bb[index + 6] & 0xff) << 48)
| (((long) bb[index + 5] & 0xff) << 40)
| (((long) bb[index + 4] & 0xff) << 32)
| (((long) bb[index + 3] & 0xff) << 24)
| (((long) bb[index + 2] & 0xff) << 16)
| (((long) bb[index + 1] & 0xff) << 8) | (((long) bb[index + 0] & 0xff) << 0));
}

/**
* float转换byte
*
* @param bb
* @param x
* @param index
*/
public static byte[] floatTobyteArray(float v) {
ByteBuffer bb = ByteBuffer.allocate(4);
byte[] ret = new byte[4];
FloatBuffer fb = bb.asFloatBuffer();
fb.put(v);
bb.get(ret);
return ret;
}

/**
* 通过byte数组取得float
*
* @param bb
* @param index
* @return
*/
public static float byteArrayToFloat(byte[] v) {
ByteBuffer bb = ByteBuffer.wrap(v);
FloatBuffer fb = bb.asFloatBuffer();
return fb.get();
}

/**
* double转换byte
*
* @param bb
* @param x
* @param index
*/
public byte[] doubleToByteArray(double x) {
ByteBuffer bb = ByteBuffer.allocate(8);
byte[] ret = new byte[8];
DoubleBuffer fb = bb.asDoubleBuffer();
fb.put(x);
bb.get(ret);
return ret;
}

/**
* 通过byte数组取得float
*
* @param bb
* @param index
* @return
*/
public double byteArrayToDouble(byte[] b) {
ByteBuffer bb = ByteBuffer.wrap(b);
DoubleBuffer fb = bb.asDoubleBuffer();
return fb.get();
}