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

实例如下：

public class DataTypeChangeHelper { 
   
  public static int unsignedByteToInt(byte b) { 
    return (int) b & 0xFF; 
  } 
 
   
  public static String byteToHex(byte b) { 
    int i = b & 0xFF; 
    return Integer.toHexString(i); 
  } 
 
   
  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; 
  } 
 
   
  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; 
  } 
 
   
  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; 
  } 
 
   
  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; 
  } 
 
   
  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; 
  } 
 
   
  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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