8个字节的16进制数 如何转换成10进制数
各路大神：
下面的方法是把10进制数转换成8个字节的16进制数：
如把 13912345678L(long型10进制数)转换成字节数组byte[] b = new byte[8],
b = {78, -116, 61, 61, 3, 0, 0, 0}
方法代码：
long l = 13912345678L;
byte [] b = new byte[8];
b[0] = (byte) (l & 0x000000000000FFL);
b[1] = (byte) ((l & 0x0000000000FF00L) >> 8);
b[2] = (byte) ((l & 0x0000000000FF0000L) >> 16);
b[3] = (byte) ((l & 0x00000000FF000000L) >> 24);
b[4] = (byte) ((l & 0x000000FF00000000L) >> 32);
b[5] = (byte) ((l & 0x0000FF0000000000L) >> 40);
b[6] = (byte) ((l & 0x00FF000000000000L) >> 48);
b[7] = (byte) ((l & 0xFF00000000000000L) >> 56);
问题来了，如何把其返回去，即由字节数组b = {78, -116, 61, 61, 3, 0, 0, 0} 转换成l=13912345678L(十进制数)？ 求高手指教呀！！！！
[解决办法]
我写了一个,参考一下:
import java.util.Arrays;public class ChangeBytesToNumber{ public static void main(String[] args) { long l = -13912345678L; byte[] b = numberToBytes(l); //数转成数组。 long number=bytesToNumber(b); //还原成数。 System.out.println("l is "+l); System.out.println("number is "+number); } public static long bytesToNumber(byte[] b) { byte[] b1=Arrays.copyOfRange(b,0,8); //复制数值部分。 StringBuffer sb=new StringBuffer(); String tem=null; int length=b1.length; for(int i=0;i<length;i++) //组成16进制字符串。 { tem=(b1[length-i-1]>=0)?Integer.toHexString(b1[length-i-1]): Integer.toHexString(b1[length-i-1]).substring(6); sb.append(tem); } long result=Long.parseLong(sb.toString(),16); //转成long型值。 result=(b[8]==0)?result:0-result; //处理符号。 return result; } public static byte[] numberToBytes(long l) { byte [] b = new byte[9]; b[8]=(l>0)?(byte)0:(byte)1; //l>0,b[8]=0；l<0，b[8]=1。 l=(l>0)?l:0-l; //处理l的绝对值。 b[0] = (byte) (l & 0x000000000000FFL); b[1] = (byte) ((l & 0x0000000000FF00L) >> 8); b[2] = (byte) ((l & 0x0000000000FF0000L) >> 16); b[3] = (byte) ((l & 0x00000000FF000000L) >> 24); b[4] = (byte) ((l & 0x000000FF00000000L) >> 32); b[5] = (byte) ((l & 0x0000FF0000000000L) >> 40); b[6] = (byte) ((l & 0x00FF000000000000L) >> 48); b[7] = (byte) ((l & 0xFF00000000000000L) >> 56); return b; }}
[解决办法]
/** * 各基础类型与byte之间的转换 * @author shanl * */public class Utility { /** * 将short转成byte[2] * @param a * @return */ public static byte[] short2Byte(short a){ byte[] b = new byte[2]; b[0] = (byte) (a >> 8); b[1] = (byte) (a); return b; } /** * 将short转成byte[2] * @param a * @param b * @param offset b中的偏移量 */ public static void short2Byte(short a, byte[] b, int offset){ b[offset] = (byte) (a >> 8); b[offset+1] = (byte) (a); } /** * 将byte[2]转换成short * @param b * @return */ public static short byte2Short(byte[] b){ return (short) (((b[0] & 0xff) << 8) | (b[1] & 0xff)); } /** * 将byte[2]转换成short * @param b * @param offset * @return */ public static short byte2Short(byte[] b, int offset){ return (short) (((b[offset] & 0xff) << 8) | (b[offset+1] & 0xff)); } /** * long转byte[8] * * @param a * @param b * @param offset * b的偏移量 */ public static void long2Byte(long a, byte[] b, int offset) { b[offset + 0] = (byte) (a >> 56); b[offset + 1] = (byte) (a >> 48); b[offset + 2] = (byte) (a >> 40); b[offset + 3] = (byte) (a >> 32); b[offset + 4] = (byte) (a >> 24); b[offset + 5] = (byte) (a >> 16); b[offset + 6] = (byte) (a >> 8); b[offset + 7] = (byte) (a); } /** * byte[8]转long * * @param b * @param offset * b的偏移量 * @return */ public static long byte2Long(byte[] b, int offset) { return ((((long) b[offset + 0] & 0xff) << 56) | (((long) b[offset + 1] & 0xff) << 48) | (((long) b[offset + 2] & 0xff) << 40) | (((long) b[offset + 3] & 0xff) << 32) | (((long) b[offset + 4] & 0xff) << 24) | (((long) b[offset + 5] & 0xff) << 16) | (((long) b[offset + 6] & 0xff) << 8) | (((long) b[offset + 7] & 0xff) << 0)); } /** * byte[8]转long * * @param b * @return */ public static long byte2Long(byte[] b) { return ((b[0]&0xff)<<56)| ((b[1]&0xff)<<48)| ((b[2]&0xff)<<40)| ((b[3]&0xff)<<32)| ((b[4]&0xff)<<24)| ((b[5]&0xff)<<16)| ((b[6]&0xff)<<8)| (b[7]&0xff); } /** * long转byte[8] * * @param a * @return */ public static byte[] long2Byte(long a) { byte[] b = new byte[4 * 2]; b[0] = (byte) (a >> 56); b[1] = (byte) (a >> 48); b[2] = (byte) (a >> 40); b[3] = (byte) (a >> 32); b[4] = (byte) (a >> 24); b[5] = (byte) (a >> 16); b[6] = (byte) (a >> 8); b[7] = (byte) (a >> 0); return b; } /** * byte数组转int * * @param b * @return */ public static int byte2Int(byte[] b) { return ((b[0] & 0xff) << 24) | ((b[1] & 0xff) << 16) | ((b[2] & 0xff) << 8) | (b[3] & 0xff); } /** * byte数组转int * * @param b * @param offset * @return */ public static int byte2Int(byte[] b, int offset) { return ((b[offset++] & 0xff) << 24) | ((b[offset++] & 0xff) << 16) | ((b[offset++] & 0xff) << 8) | (b[offset++] & 0xff); } /** * int转byte数组 * * @param a * @return */ public static byte[] int2Byte(int a) { byte[] b = new byte[4]; b[0] = (byte) (a >> 24); b[1] = (byte) (a >> 16); b[2] = (byte) (a >> 8); b[3] = (byte) (a); return b; } /** * int转byte数组 * * @param a * @param b * @param offset * @return */ public static void int2Byte(int a, byte[] b, int offset) { b[offset++] = (byte) (a >> 24); b[offset++] = (byte) (a >> 16); b[offset++] = (byte) (a >> 8); b[offset++] = (byte) (a); }}