Java字节序,java整型数与网络字节序 byte[] 数组转换关系(ByteArrayOutputStream用法)

/**
* 通信格式转换
*
* Java和一些windows编程语言如c、c++、delphi所写的网络程序进行通讯时，需要进行相应的转换
* 高、低字节之间的转换
* windows的字节序为低字节开头
* linux,unix的字节序为高字节开头
* java则无论平台变化，都是高字节开头
  */

public class FormatTransfer {
/**
  * 将int转为低字节在前，高字节在后的byte数组
  * @param n int
  * @return byte[]
  */
public static byte[] toLH(int n) {
  byte[] b = new byte[4];
  b[0] = (byte) (n & 0xff);
  b[1] = (byte) (n >> 8 & 0xff);
  b[2] = (byte) (n >> 16 & 0xff);
  b[3] = (byte) (n >> 24 & 0xff);
  return b;
}

/**
  * 将int转为高字节在前，低字节在后的byte数组
  * @param n int
  * @return byte[]
  */
public static byte[] toHH(int n) {
  byte[] b = new byte[4];
  b[3] = (byte) (n & 0xff);
  b[2] = (byte) (n >> 8 & 0xff);
  b[1] = (byte) (n >> 16 & 0xff);
  b[0] = (byte) (n >> 24 & 0xff);
  return b;
}

/**
  * 将short转为低字节在前，高字节在后的byte数组
  * @param n short
  * @return byte[]
  */
public static byte[] toLH(short n) {
  byte[] b = new byte[2];
  b[0] = (byte) (n & 0xff);
  b[1] = (byte) (n >> 8 & 0xff);
  return b;
}

/**
  * 将short转为高字节在前，低字节在后的byte数组
  * @param n short
  * @return byte[]
  */
public static byte[] toHH(short n) {
  byte[] b = new byte[2];
  b[1] = (byte) (n & 0xff);
  b[0] = (byte) (n >> 8 & 0xff);
  return b;
}



/**
  * 将将int转为高字节在前，低字节在后的byte数组

public static byte[] toHH(int number) {
  int temp = number;
  byte[] b = new byte[4];
  for (int i = b.length - 1; i > -1; i--) {
    b = new Integer(temp & 0xff).byteValue();
    temp = temp >> 8;
  }
  return b;
}

public static byte[] IntToByteArray(int i) {
    byte[] abyte0 = new byte[4];
    abyte0[3] = (byte) (0xff & i);
    abyte0[2] = (byte) ((0xff00 & i) >> 8);
    abyte0[1] = (byte) ((0xff0000 & i) >> 16);
    abyte0[0] = (byte) ((0xff000000 & i) >> 24);
    return abyte0;
}


*/

/**
  * 将float转为低字节在前，高字节在后的byte数组
  */
public static byte[] toLH(float f) {
  return toLH(Float.floatToRawIntBits(f));
}

/**
  * 将float转为高字节在前，低字节在后的byte数组
  */
public static byte[] toHH(float f) {
  return toHH(Float.floatToRawIntBits(f));
}

/**
  * 将String转为byte数组
  */
public static byte[] stringToBytes(String s, int length) {
  while (s.getBytes().length < length) {
    s += " ";
  }
  return s.getBytes();
}


/**
  * 将字节数组转换为String
  * @param b byte[]
  * @return String
  */
public static String bytesToString(byte[] b) {
  StringBuffer result = new StringBuffer("");
  int length = b.length;
  for (int i=0; i<length; i++) {
    result.append((char)(b & 0xff));
  }
  return result.toString();
}

/**
  * 将字符串转换为byte数组
  * @param s String
  * @return byte[]
  */
public static byte[] stringToBytes(String s) {
  return s.getBytes();
}

/**
  * 将高字节数组转换为int
  * @param b byte[]
  * @return int
  */
public static int hBytesToInt(byte[] b) {
  int s = 0;
  for (int i = 0; i < 3; i++) {
    if (b >= 0) {
    s = s + b;
    } else {
    s = s + 256 + b;
    }
    s = s * 256;
  }
  if (b[3] >= 0) {
    s = s + b[3];
  } else {
    s = s + 256 + b[3];
  }
  return s;
}

/**
  * 将低字节数组转换为int
  * @param b byte[]
  * @return int
  */
public static int lBytesToInt(byte[] b) {
  int s = 0;
  for (int i = 0; i < 3; i++) {
    if (b[3-i] >= 0) {
    s = s + b[3-i];
    } else {
    s = s + 256 + b[3-i];
    }
    s = s * 256;
  }
  if (b[0] >= 0) {
    s = s + b[0];
  } else {
    s = s + 256 + b[0];
  }
  return s;
}


/**
  * 高字节数组到short的转换
  * @param b byte[]
  * @return short
  */
public static short hBytesToShort(byte[] b) {
  int s = 0;
  if (b[0] >= 0) {
    s = s + b[0];
    } else {
    s = s + 256 + b[0];
    }
    s = s * 256;
  if (b[1] >= 0) {
    s = s + b[1];
  } else {
    s = s + 256 + b[1];
  }
  short result = (short)s;
  return result;
}

/**
  * 低字节数组到short的转换
  * @param b byte[]
  * @return short
  */
public static short lBytesToShort(byte[] b) {
  int s = 0;
  if (b[1] >= 0) {
    s = s + b[1];
    } else {
    s = s + 256 + b[1];
    }
    s = s * 256;
  if (b[0] >= 0) {
    s = s + b[0];
  } else {
    s = s + 256 + b[0];
  }
  short result = (short)s;
  return result;
}

/**
  * 高字节数组转换为float
  * @param b byte[]
  * @return float
  */
public static float hBytesToFloat(byte[] b) {
  int i = 0;
  Float F = new Float(0.0);
  i = ((((b[0]&0xff)<<8 | (b[1]&0xff))<<8) | (b[2]&0xff))<<8 | (b[3]&0xff);
  return F.intBitsToFloat(i);
}

/**
  * 低字节数组转换为float
  * @param b byte[]
  * @return float
  */
public static float lBytesToFloat(byte[] b) {
  int i = 0;
  Float F = new Float(0.0);
  i = ((((b[3]&0xff)<<8 | (b[2]&0xff))<<8) | (b[1]&0xff))<<8 | (b[0]&0xff);
  return F.intBitsToFloat(i);
}

/**
  * 将byte数组中的元素倒序排列
  */
public static byte[] bytesReverseOrder(byte[] b) {
  int length = b.length;
  byte[] result = new byte[length];
  for(int i=0; i<length; i++) {
    result[length-i-1] = b;
  }
  return result;
}

/**
  * 打印byte数组
  */
public static void printBytes(byte[] bb) {
  int length = bb.length;
  for (int i=0; i<length; i++) {
    System.out.print(bb + " ");
  }
  System.out.println("");
}

public static void logBytes(byte[] bb) {
  int length = bb.length;
  String out = "";
  for (int i=0; i<length; i++) {
    out = out + bb + " ";
  }

}

/**
  * 将int类型的值转换为字节序颠倒过来对应的int值
  * @param i int
  * @return int
  */
public static int reverseInt(int i) {
  int result = FormatTransfer.hBytesToInt(FormatTransfer.toLH(i));
  return result;
}

/**
  * 将short类型的值转换为字节序颠倒过来对应的short值
  * @param s short
  * @return short
  */
public static short reverseShort(short s) {
  short result = FormatTransfer.hBytesToShort(FormatTransfer.toLH(s));
  return result;
}

/**
  * 将float类型的值转换为字节序颠倒过来对应的float值
  * @param f float
  * @return float
  */
public static float reverseFloat(float f) {
  float result = FormatTransfer.hBytesToFloat(FormatTransfer.toLH(f));
  return result;
}

}

 

java整型数与网络字节序的 byte[] 数组转换关系

http://www.cnblogs.com/devinzhang/archive/2012/09/28/2707605.html

工作项目需要在java和c/c++之间进行socket通信，socket通信是以字节流或者字节包进行的，socket发送方须将数据转换为字节流或者字节包，而接收方则将字节流和字节包再转换回相应的数据类型。如果发送方和接收方都是同种语言，则一般只涉及到字节序的调整。而对于java和c/c++的通信，则情况就要复杂一些，主要是因为java中没有unsigned类型，并且java和c在某些数据类型上的长度不一致。
　　本文就是针对这种情况，整理了java数据类型和网络字节流或字节包(相当于java的byte数组)之间转换方法。实际上网上这方面的资料不少，但往往不全，甚至有些有错误，于是就花了点时间对java整型数和网络字节序的byte[]之间转换的各种情况做了一些验证和整理。整理出来的函数如下：

public class ByteConvert {
    // 以下 是整型数 和 网络字节序的  byte[] 数组之间的转换
    public static byte[] longToBytes(long n) {
        byte[] b = new byte[8];
        b[7] = (byte) (n & 0xff);
        b[6] = (byte) (n >> 8  & 0xff);
        b[5] = (byte) (n >> 16 & 0xff);
        b[4] = (byte) (n >> 24 & 0xff);
        b[3] = (byte) (n >> 32 & 0xff);
        b[2] = (byte) (n >> 40 & 0xff);
        b[1] = (byte) (n >> 48 & 0xff);
        b[0] = (byte) (n >> 56 & 0xff);
        return b;
    }

    public static void longToBytes( long n, byte[] array, int offset ){
        array[7+offset] = (byte) (n & 0xff);
        array[6+offset] = (byte) (n >> 8 & 0xff);
        array[5+offset] = (byte) (n >> 16 & 0xff);
        array[4+offset] = (byte) (n >> 24 & 0xff);
        array[3+offset] = (byte) (n >> 32 & 0xff);
        array[2+offset] = (byte) (n >> 40 & 0xff);
        array[1+offset] = (byte) (n >> 48 & 0xff);
        array[0+offset] = (byte) (n >> 56 & 0xff);
    }

    public static long bytesToLong( byte[] array )
    {
        return ((((long) array[ 0] & 0xff) << 56)
              | (((long) array[ 1] & 0xff) << 48)
              | (((long) array[ 2] & 0xff) << 40)
              | (((long) array[ 3] & 0xff) << 32)
              | (((long) array[ 4] & 0xff) << 24)
              | (((long) array[ 5] & 0xff) << 16)
              | (((long) array[ 6] & 0xff) << 8)
              | (((long) array[ 7] & 0xff) << 0));
    }

    public static long bytesToLong( byte[] array, int offset )
    {
        return ((((long) array[offset + 0] & 0xff) << 56)
              | (((long) array[offset + 1] & 0xff) << 48)
              | (((long) array[offset + 2] & 0xff) << 40)
              | (((long) array[offset + 3] & 0xff) << 32)
              | (((long) array[offset + 4] & 0xff) << 24)
              | (((long) array[offset + 5] & 0xff) << 16)
              | (((long) array[offset + 6] & 0xff) << 8)
              | (((long) array[offset + 7] & 0xff) << 0));
    }

    public static byte[] intToBytes(int n) {
        byte[] b = new byte[4];
        b[3] = (byte) (n & 0xff);
        b[2] = (byte) (n >> 8 & 0xff);
        b[1] = (byte) (n >> 16 & 0xff);
        b[0] = (byte) (n >> 24 & 0xff);
        return b;
    }

    public static void intToBytes( int n, byte[] array, int offset ){
        array[3+offset] = (byte) (n & 0xff);
        array[2+offset] = (byte) (n >> 8 & 0xff);
        array[1+offset] = (byte) (n >> 16 & 0xff);
        array[offset] = (byte) (n >> 24 & 0xff);
    }

    public static int bytesToInt(byte b[]) {
        return    b[3] & 0xff
               | (b[2] & 0xff) << 8
               | (b[1] & 0xff) << 16
               | (b[0] & 0xff) << 24;
    }

    public static int bytesToInt(byte b[], int offset) {
        return    b[offset+3] & 0xff
               | (b[offset+2] & 0xff) << 8
               | (b[offset+1] & 0xff) << 16
               | (b[offset] & 0xff) << 24;
    }

    public static byte[] uintToBytes( long n )
    {
        byte[] b = new byte[4];
        b[3] = (byte) (n & 0xff);
        b[2] = (byte) (n >> 8 & 0xff);
        b[1] = (byte) (n >> 16 & 0xff);
        b[0] = (byte) (n >> 24 & 0xff);

        return b;
    }

    public static void uintToBytes( long n, byte[] array, int offset ){
        array[3+offset] = (byte) (n );
        array[2+offset] = (byte) (n >> 8 & 0xff);
        array[1+offset] = (byte) (n >> 16 & 0xff);
        array[offset]   = (byte) (n >> 24 & 0xff);
    }

    public static long bytesToUint(byte[] array) {
        return ((long) (array[3] & 0xff))
             | ((long) (array[2] & 0xff)) << 8
             | ((long) (array[1] & 0xff)) << 16
             | ((long) (array[0] & 0xff)) << 24;
    }

    public static long bytesToUint(byte[] array, int offset) {
        return ((long) (array[offset+3] & 0xff))
              | ((long) (array[offset+2] & 0xff)) << 8
             | ((long) (array[offset+1] & 0xff)) << 16
             | ((long) (array[offset]   & 0xff)) << 24;
    }

    public static byte[] shortToBytes(short n) {
        byte[] b = new byte[2];
        b[1] = (byte) ( n       & 0xff);
        b[0] = (byte) ((n >> 8) & 0xff);
        return b;
    }

    public static void shortToBytes(short n, byte[] array, int offset ) {
        array[offset+1] = (byte) ( n       & 0xff);
        array[offset] = (byte) ((n >> 8) & 0xff);
    }

    public static short bytesToShort(byte[] b){
        return (short)( b[1] & 0xff
                      |(b[0] & 0xff) << 8 );
    }

    public static short bytesToShort(byte[] b, int offset){
        return (short)( b[offset+1] & 0xff
                      |(b[offset]    & 0xff) << 8 );
    }

    public static byte[] ushortToBytes(int n) {
        byte[] b = new byte[2];
        b[1] = (byte) ( n       & 0xff);
        b[0] = (byte) ((n >> 8) & 0xff);
        return b;
    }

    public static void ushortToBytes(int n, byte[] array, int offset ) {
        array[offset+1] = (byte) ( n       & 0xff);
        array[offset] = (byte)   ((n >> 8) & 0xff);
    }

    public static int bytesToUshort(byte b[]) {
        return    b[1] & 0xff
               | (b[0] & 0xff) << 8;
    }

    public static int bytesToUshort(byte b[], int offset) {
        return    b[offset+1] & 0xff
               | (b[offset]   & 0xff) << 8;
    }

    public static byte[] ubyteToBytes( int n ){
        byte[] b = new byte[1];
        b[0] = (byte) (n & 0xff);
        return b;
    }

    public static void ubyteToBytes( int n, byte[] array, int offset ){
        array[0] = (byte) (n & 0xff);
    }

    public static int bytesToUbyte( byte[] array ){
        return array[0] & 0xff;
    }

    public static int bytesToUbyte( byte[] array, int offset ){
        return array[offset] & 0xff;
    }
    // char 类型、 float、double 类型和 byte[] 数组之间的转换关系还需继续研究实现。
}


测试程序如下：

public class ByteConvertTest {

    public static String byte2Hex(byte[] buf)
    {
        StringBuffer strbuf = new StringBuffer();
        strbuf.append("{");
        for (byte b : buf)
        {
            if (b == 0)
            {
                strbuf.append("00");
            }
            else if (b == -1)
            {
                strbuf.append("FF");
            }
            else
            {
                String str = Integer.toHexString(b).toUpperCase();
                // sb.append(a);
                if (str.length() == 8)
                {
                    str = str.substring(6, 8);
                }
                else if (str.length() < 2)
                {
                    str = "0" + str;
                }
                strbuf.append(str);
            }
            strbuf.append(" ");
        }
        strbuf.append("}");
        return strbuf.toString();
    }

    public static byte[] longToBytes(long n) {
        byte[] b = new byte[8];
        b[7] = (byte) (n & 0xff);
        b[6] = (byte) (n >> 8  & 0xff);
        b[5] = (byte) (n >> 16 & 0xff);
        b[4] = (byte) (n >> 24 & 0xff);
        b[3] = (byte) (n >> 32 & 0xff);
        b[2] = (byte) (n >> 40 & 0xff);
        b[1] = (byte) (n >> 48 & 0xff);
        b[0] = (byte) (n >> 56 & 0xff);
        return b;
    }

    public static long bytesToLong( byte[] array )
    {
        return ((((long) array[ 0] & 0xff) << 56)
              | (((long) array[ 1] & 0xff) << 48)
              | (((long) array[ 2] & 0xff) << 40)
              | (((long) array[ 3] & 0xff) << 32)
              | (((long) array[ 4] & 0xff) << 24)
              | (((long) array[ 5] & 0xff) << 16)
              | (((long) array[ 6] & 0xff) << 8)
              | (((long) array[ 7] & 0xff) ));
    }

    public static int bytesToInt(byte b[]) {
        return    b[3] & 0xff
               | (b[2] & 0xff) << 8
               | (b[1] & 0xff) << 16
               | (b[0] & 0xff) << 24;
    }

    public static long bytesToUint(byte[] array) {
        return ((long) (array[3] & 0xff))
             | ((long) (array[2] & 0xff)) << 8
             | ((long) (array[1] & 0xff)) << 16
             | ((long) (array[0] & 0xff)) << 24;
    }

    public static byte[] uintToBytes( long n )
    {
        byte[] b = new byte[4];
        b[3] = (byte) (n & 0xff);
        b[2] = (byte) (n >> 8 & 0xff);
        b[1] = (byte) (n >> 16 & 0xff);
        b[0] = (byte) (n >> 24 & 0xff);

        return b;
    }


    public static byte[] shortToBytes(short n) {
        byte[] b = new byte[2];
        b[1] = (byte) ( n       & 0xff);
        b[0] = (byte) ((n >> 8) & 0xff);
        return b;
    }

    public static short bytesToShort(byte[] b){
        return (short)( b[1] & 0xff
                      |(b[0] & 0xff) << 8 );
    }

    static void testShortConvert(){
        System.out.println("=================== short convert =============");
        System.out.println("byte2Hex(shortToBytes((short)0x11f2))"+byte2Hex(shortToBytes((short)0x11f2)));
        System.out.print("println 0x11f2:");
        System.out.println((short)0x11f2);
        System.out.println("byte2Hex(shortToBytes((short)0xf1f2))"+byte2Hex(shortToBytes((short)0xf1f2)));
        System.out.print("println 0xf1f2:");
        System.out.println((short)0xf1f2);
        System.out.print("println bytesToShort(shortToBytes((short)0x11f2)):");
        System.out.println((short)bytesToShort(shortToBytes((short)0x11f2)));
        System.out.print("println bytesToShort(shortToBytes((short)0xf1f2)):");
        System.out.println((short)bytesToShort(shortToBytes((short)0xf1f2)));
    }


    public static byte[] ushortToBytes(int n) {
        byte[] b = new byte[2];
        b[1] = (byte) (n & 0xff);
        b[0] = (byte) (n >> 8 & 0xff);
        return b;
    }


    public static int bytesToUshort(byte b[]) {
        return    b[1] & 0xff
               | (b[0] & 0xff) << 8;
    }

    static void testUshortConvert(){
        System.out.println("=================== Ushort convert =============");
        System.out.println("byte2Hex(ushortToBytes(0x11f2))"+byte2Hex(ushortToBytes(0x11f2)));
        System.out.print("println 0x11f2:");
        System.out.println(0x11f2);
        System.out.println("byte2Hex(ushortToBytes(0xf1f2))"+byte2Hex(ushortToBytes(0xf1f2)));
        System.out.print("println 0xf1f2:");
        System.out.println(0xf1f2);
        System.out.print("println bytesToUshort(ushortToBytes(0x11f2)):");
        System.out.println(bytesToUshort(ushortToBytes(0x11f2)));
        System.out.print("println bytesToUshort(ushortToBytes(0xf1f2)):");
        System.out.println(bytesToUshort(ushortToBytes(0xf1f2)));
    }

    public static byte[] ubyteToBytes( int n ){
        byte[] b = new byte[1];
        b[0] = (byte) (n & 0xff);
        return b;
    }

    public static int bytesToUbyte( byte[] array ){
        return array[0] & 0xff;
    }

    static void testUbyteConvert(){
        System.out.println("=================== Ubyte convert =============");
        System.out.println("byte2Hex(ubyteToBytes(0x1112))"+byte2Hex(ubyteToBytes(0x1112)));
        System.out.print("println 0x1112:");
        System.out.println(0x1112);
        System.out.println("byte2Hex(ubyteToBytes(0xf2))"+byte2Hex(ubyteToBytes(0xf2)));
        System.out.print("println 0xf2:");
        System.out.println(0xf2);
        System.out.print("println bytesToUbyte(ubyteToBytes(0x1112)):");
        System.out.println(bytesToUbyte(ubyteToBytes(0x1112)));
        System.out.print("println bytesToUbyte(ubyteToBytes(0xf1f2)):");
        System.out.println(bytesToUbyte(ubyteToBytes(0xf1f2)));
    }


    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        byte[] array = new byte[4];
        array[3] = (byte) 0xF4;
        array[2] = 0x13;
        array[1] = 0x12;
        array[0] = 0x11;

        System.out.println("=================== Integer bytes =============");

        System.out.println("the bytes is:"+byte2Hex(array) );
        System.out.print("println bytesToInt :");
        System.out.println( bytesToInt(array));
        System.out.printf("printf bytesToInt :%X\n", bytesToInt(array));

        System.out.println("=================== long bytes =============");
        byte[] longBytes = new byte[8];

        longBytes[7] = (byte) 0xf7;
        longBytes[6] = (byte) 0x16;
        longBytes[5] = (byte) 0xf5;
        longBytes[4] = (byte) 0x14;
        longBytes[3] = (byte) 0xf3;
        longBytes[2] = (byte) 0x12;
        longBytes[1] = (byte) 0xf1;
        longBytes[0] = (byte) 0x10;


        System.out.println( "the bytes is:"+byte2Hex(longBytes) );
        System.out.printf("printf bytesToLong:%X\n",bytesToLong(longBytes));

        System.out.println("=================byte to long ================");

        byte b = (byte)0xf1;
        System.out.print("Println the byte:");
        System.out.println(b);
        System.out.printf("Printf the byte:%X\n",b);
        long l = b;
        System.out.print("Println byte to long:");
        System.out.println(l);
        System.out.printf("printf byte to long:%X\n",l);

        System.out.println("================= uint Bytes ================");

        byte[] uint = new byte[4];
        uint[3] = (byte) 0xf3;
        uint[2] = (byte) 0x12;
        uint[1] = (byte) 0xf1;
        uint[0] = (byte) 0xFF;

        System.out.println( "the bytes is:"+byte2Hex(uint) );
        System.out.printf("printf bytesToUint:%X\n",bytesToUint(uint));
        System.out.print("Println bytesToUint:");
        System.out.println(bytesToUint(uint));
        System.out.println("byte2Hex(uintToBytes(0x11f2f3f4f5f6f7f8l)):"+byte2Hex(uintToBytes(0x11f2f3f4f5f6f7f8l)));

        System.out.println("===============Long Integer==============");
        System.out.print("println 0x11f2f3f4f5f6f7f8l:");
        System.out.println(0x11f2f3f4f5f6f7f8l);
        System.out.printf("Printf 0x11f2f3f4f5f6f7f8l:%X\n",0x11f2f3f4f5f6f7f8l);
        System.out.println("println byte2Hex(longToBytes(0x11f2f3f4f5f6f7f8l))"+byte2Hex(longToBytes(0x11f2f3f4f5f6f7f8l)));
        // 注意，下面的这行，并不能获得正确的uint。
        System.out.printf("printf bytesToUint(longToBytes(0x11f2f3f4f5f6f7f8l):%X\n",bytesToUint(longToBytes(0x11f2f3f4f5f6f7f8l)));

        System.out.println("===============bytesToLong(longToBytes())==============");
        System.out.println(bytesToLong(longToBytes(0x11f2f3f4f5f6f7f8l)));
        System.out.printf("%X\n",bytesToLong(longToBytes(0x11f2f3f4f5f6f7f8l)));

        testShortConvert();
        testUshortConvert();
        testUbyteConvert();
    }

}

java中int与byte〔4〕的相互转换

http://www.cnblogs.com/mayola/archive/2011/11/17/2253101.html

我们都知道，JAVA中的基本数据类型有int,byte,char,long,float,double...，它们与引用数据类型很不一样，之所有在如此面向对象的JAVA语言中依然支持这些值类型，就是考虑到性能的原因。现在，同样是因为考虑到性能，我们需要一种高效的方法使int与byte[]能够自由的相互转换，理由就是，我们需要在网络上传送数据，而网络上的数据都是byte数据流，这就需要一个int-> byte[]与byte[] -> int的方法。
　　简单的方法，我们可以用DataOutputStream与ByteArrayOutputStream来将int转换成byte[]，方法就是：
        int i = 0;
        ByteArrayOutputStream boutput = newByteArrayOutputStream();
        DataOutputStream doutput = newDataOutputStream(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 = newByteArrayInputStream(buf);
        DataInputStream dintput = new DataInputStream();
         int i = dintput.readInt();
　　上面的方法可以达到int<->byte[]的转化，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。

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;
}

 

ByteArrayOutputStream用法

字节数组流：
ByteArrayOutputStream: 可以捕获内存缓冲区的数据，转换成字节数组。
ByteArrayoutputStream bout=new ByteArrayOutputStream();
bout.write(int a); bout.write(int b); bout.write(int c);
byte[] buf=bout.toByteArray();//获取内存缓冲中的数据
for(int i=0;i<=buf.length;i++)
{
System.out.println(buf);
}
bout.close();
注：通过调用reset（）方法可以重新定位。
ByteArrayInputStream: 可以将字节数组转化为输入流
ByteArrayInputStream bin=new ByteArrayInputStream(byte[] buf);
int data=0;
while( (b=bin.read())!=-1)
{
System.out.println(b);
}
bin.close();

与DataOutputStream&DataInputStream联合使用：

ByteArrayOutputStream bout=new ByteArrayOutputStream();
DataOutputStream dos=new DataOutputStream(bout);
String name="suntao";
int age=19;
dos.writeUTF(name);
dos.writeInt(age);
byte[] buf=bout.toByteArray();//获取内存缓冲区中的数据
dos.close();
bout.close();

ByteArrayInputStream bin=new ByteArrayInputStream(byte[] buf);
DataInputStream dis=new DataInputStream(bin);
String name=dis.readUTF();//从字节数组中读取
int age=dis.readInt();
dis.close();
bin.close();

注: DataInputStream&DataOutputStream还可以与FileInputStream&FileOutputStream
联合使用。
其中：
DataInputStream&DataOutputStream关心如何将数据从高层次的形式转化成低层次的形式.
FileInputStream&FileOutputStream关心如何操作存储单元以接受和产生数据。

 

JAVA里面关于byte数组和String之间的转换问题

JAVA里面关于byte数组和String之间的转换问题 
　　引自：http://soniccyj.bokee.com/6175850.html 
　　JAVA里面关于byte数组和String之间的转换问题 
　　把byte转化成string，必须经过编码。 
　　例如下面一个例子: 
　　import java.io.UnsupportedEncodingException; 
　　public class test{ 
　　public static void main(String g[]) { 
　　String s = "12345abcd"; 
　　byte b[] = s.getBytes(); 
　　String t = b.toString(); 
　　System.out.println(t); 
　　} 
　　} 
　　输出字符串的结果和字符串s不一样了. 
　　经过以下方式转码就可以正确转换了: 
　　public class test{ 
　　public static void main(String g[]) { 
　　String s = "12345abcd"; 
　　byte b[] = s.getBytes(); 
　　try { 
　　String t = new String(b); 
　　System.out.print(t); 
　　} catch (Exception e) { 
　　e.printStackTrace(); 
　　} 
　　} 
　　} 
　　引自：http://topic.csdn.net/t/20050404/10/3906398.html 
　　String str = "String"; 
　　byte[] byte1 = str.getBytes(); 
　　String str1 = new String(byte1); 
　　byte[] byte2 = str1.getBytes(); 
　　String str2 = new String(byte2); 
　　System.out.println("str<<<" + str); 
　　System.out.println("byte1<<<" + byte1); 
　　System.out.println("str1<<<" + str1); 
　　System.out.println("byte2<<<" + byte2); 
　　System.out.println("str2<<<" + str2); 
　　------------------------------------- 
　　输出结果 
　　str<<<String 
　　byte1<<<[B@192d342 
　　str1<<<String 
　　byte2<<<[B@6b97fd 
　　str2<<<String 
　　想请教为什么两个byte输出的不一样呢? 
　　String str = "String"; 
　　byte[] byte1 = str.getBytes(); 
　　String str1 = new String(byte1); 
　　byte[] byte2 = str1.getBytes(); 
　　---------- 
　　注意byte1是str得到的byte数组，而byte2是另一个字符串str1得到的数组 
　　他们本身也是两个对象 
　　直接打印实际上调用的是toString()方法，而toString()的默认实现是打印对象类型+hashCode() 
　　[B表示byte数组 
　　@表示之后的是地址 
　　后面跟着的是hashCode，其实就是其虚拟机地址 
　　所以这个结果也就是顺理成章了.

最近的项目中要使用到把byte[]类型转换成String字符串然后通过网络发送，但发现发现出去的字符串和获取的字符串虽然是一样的，但当用String的getBytes()的方法得到的byte[]跟原来的byte[]是不一样的。

看如下代码：

 

bytebytes[] = new byte[] { 50, 0, -1, 28, -24 };

String string = new String(bytes);

byte[] ret = string.getBytes();

查看ret的数据发现是50, 0, -17, -65, -67, 28, -17, -65, -67,发现数据并不是原来的数据。

而使用如下代码就可以得到原来的数据：

 

bytebytes[] = new byte[] { 50, 0, -1, 28, -24 };

 

 

StringisoString = new String(bytes, "ISO-8859-1");

byte[] isoret = isoString.getBytes("ISO-8859-1");

这是为什么呢？原因是第一种方法默认是用UTF-8编码来生成String的，用System.getProperty("sun.jnu.encoding")可以得到Android默认编码是UTF-8。UTF-8是可变长度的编码，原来的字节数组就被改变了。而ISO8859-1通常叫做Latin-1，Latin-1包括了书写所有西方欧洲语言不可缺少的附加字符，其中 0~127的字符与ASCII码相同，它是单字节的编码方式，这样第二种方式生成的String里的字节数组就跟原来的字节数组一样。在new String使用其他编码如GBK,GB2312的话一样也会导致字节数组发生变化，因此要想获取String里单字节数组，就应该使用iso8859-1编码。

评论

1 楼 GGGGeek 2017-09-21  

这总结的是相当详细了，可惜博主再也没有更新过博客了。。。