学步园

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();
 }