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,無符號右移。 
return targets; 
} 

public static int byte2int(byte[] res) { 
// 一個byte數據左移24位變成0x??000000，再右移8位變成0x00??0000 

int targets = (res[0] & 0xff) | ((res[1] << 8) & 0xff00) // | 表示安位或 
| ((res[2] << 24) >>> 8) | (res[3] << 24); 
return targets; 
} 

public static void main(String[] args) { 
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
    DataOutputStream dos = new DataOutputStream(baos); 
    try { 
      dos.writeByte(4); 
      dos.writeByte(1); 
      dos.writeByte(1); 
      dos.writeShort(217); 
     } catch (IOException e) { 
    e.printStackTrace(); 
  } 
 
  byte[] aa = baos.toByteArray(); 
  ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray()); 
  DataInputStream dis = new DataInputStream(bais); 
 
  try { 
    System.out.println(dis.readByte()); 
    System.out.println(dis.readByte()); 
    System.out.println(dis.readByte()); 
    System.out.println(dis.readShort()); 
  } catch (IOException e) { 
    e.printStackTrace(); 
  } 
  try { 
    dos.close(); 
    dis.close(); 
  } catch (IOException e) { 
    e.printStackTrace(); 
  } 
}