Java字节序
/**
* 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
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
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：
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。
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