java byte数组与int,long,short,byte的转换实现方法

实例如下：

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 (int) 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 & ((int) buf[index])); 
    secondbyte = (0x000000ff & ((int) buf[index + 1])); 
    thirdbyte = (0x000000ff & ((int) buf[index + 2])); 
    fourthbyte = (0x000000ff & ((int) buf[index + 3])); 
    index = index + 4; 
    return ((long) (firstbyte << 24 | secondbyte << 16 | thirdbyte << 8 | fourthbyte)) & 0xffffffffl; 
  } 
 
  /** 
   * 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; 
  } 
} 

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