java中int与byte的相互转换

      int i = 0;
      ByteArrayOutputStream boutput = new ByteArrayOutputStream();
      DataOutputStream doutput = new DataOutputStream(boutput);
      doutput.writeInt(i);
      byte[] buf = boutput.toByteArray();
  
 

执行相反的过程我们就可以将byte[]->int，我们要用到DataInputStream与ByteArrayInputStream。

      byte[] buf = new byte[4];
      ByteArrayInputStream bintput = new ByteArrayInputStream(buf);
      DataInputStream dintput = new DataInputStream();
      int i = dintput.readInt();
  
 

下面还有更加高效的方法，虽然看起来会比较费劲一些，但是性能的提升是显而易见的。

注：numberOfLeadingZeros(int i) 在指定 int 值的二进制补码表示形式中最高位(最左边)的 1 位之前,返回零位的数量

      //int -> byte[]
      privatebyte[] intToByteArray(final int integer) {
      int byteNum = (40 -Integer.numberOfLeadingZeros (integer < 0 ? ~integer : integer))/ 8;
      byte[] byteArray = new byte[4];
      for (int n = 0; n < byteNum; n++)
      byteArray[3 - n] = (byte) (integer>>> (n * 8));
      return (byteArray);
      }
      //byte[] -> int
      public static int byteArrayToInt(byte[] b, int offset) {
            int value= 0;
            for (int i = 0; i < 4; i++) {
                int shift= (4 - 1 - i) * 8;
                 value +=(b[i + offset] & 0x000000FF) << shift;
             }
            return value;
       }
  
 

      import java.io.*;
      public class IOTest {
      public static void main(String[] args) throws Exception {
        int i = 65535;
        byte[] b = intToByteArray1(i);
        for(byte bb : b) {
         System.out.print(bb + " ");
        }
      }
      public static byte[] intToByteArray1(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;
      }
      public static byte[] intToByteArray2(int i) throws Exception {
        ByteArrayOutputStream buf = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream(buf);
        out.writeInt(i);
        byte[] b = buf.toByteArray();
        out.close();
        buf.close();
        return b;
      }
  
 

文章来源: panda1234lee.blog.csdn.net，作者：panda1234lee，版权归原作者所有，如需转载，请联系作者。

原文链接：panda1234lee.blog.csdn.net/article/details/8691586