Byte和int之間的轉換
/**
*將32位的int值放到4字節的里
* @param num
* @return
*/
public static byte[] int2byteArray(int num) {
byte[] result = new byte[4];
result[0] = (byte)(num >>> 24);//取最高8位放到0下標
result[1] = (byte)(num >>> 16);//取次高8為放到1下標
result[2] = (byte)(num >>> 8); //取次低8位放到2下標
result[3] = (byte)(num ); //取最低8位放到3下標
return result;
}
/**
* 將4字節的byte數組轉成一個int值
* @param b
* @return
*/
public static int byteArray2int(byte[] b){
byte[] a = new byte[4];
int i = a.length - 1,j = b.length - 1;
for (; i >= 0; i--,j--) {//從b的尾部(即int值的低位)開始copy數據
if(j >= 0)
a[i] = b[j];
else
a[i] = 0;//如果b.length不足4,則將高位補0
}
int v0 = (a[0] & 0xff) << 24;//&0xff將byte值無差異轉成int,避免Java自動類型提升后,會保留高位的符號位
int v1 = (a[1] & 0xff) << 16;
int v2 = (a[2] & 0xff) << 8;
int v3 = (a[3] & 0xff) ;
return v0 + v1 + v2 + v3;
}
short和byte的互轉
/**
* 轉換short為byte
*
* @param b
* @param s 需要轉換的short
* @param index
*/
public static void putShort(byte b[], short s, int index) {
b[index + 1] = (byte) (s >> 8);
b[index + 0] = (byte) (s >> 0);
}
/**
* 通過byte數組取到short
*
* @param b
* @param index 第幾位開始取
* @return
*/
public static short getShort(byte[] b, int index) {
return (short) (((b[index + 1] << 8) | b[index + 0] & 0xff));
}
byte和char類型的轉換
/**
* 字符到字節轉換
*
* @param ch
* @return
*/
public static void putChar(byte[] bb, char ch, int index) {
int temp = (int) ch;
// byte[] b = new byte[2];
for (int i = 0; i < 2; i ++ ) {
// 將最高位保存在最低位
bb[index + i] = new Integer(temp & 0xff).byteValue();
temp = temp >> 8; // 向右移8位
}
}
/**
* 字節到字符轉換
*
* @param b
* @return
*/
public static char getChar(byte[] b, int index) {
int s = 0;
if (b[index + 1] > 0)
s += b[index + 1];
else
s += 256 + b[index + 0];
s *= 256;
if (b[index + 0] > 0)
s += b[index + 1];
else
s += 256 + b[index + 0];
char ch = (char) s;
return ch;
}
byte和float的轉換
/**
* float轉換byte
*
* @param bb
* @param x
* @param index
*/
public static void putFloat(byte[] bb, float x, int index) {
// byte[] b = new byte[4];
int l = Float.floatToIntBits(x);
for (int i = 0; i < 4; i++) {
bb[index + i] = new Integer(l).byteValue();
l = l >> 8;
}
}
/**
* 通過byte數組取得float
*
* @param bb
* @param index
* @return
*/
public static float getFloat(byte[] b, int index) {
int l;
l = b[index + 0];
l &= 0xff;
l |= ((long) b[index + 1] << 8);
l &= 0xffff;
l |= ((long) b[index + 2] << 16);
l &= 0xffffff;
l |= ((long) b[index + 3] << 24);
return Float.intBitsToFloat(l);
}
byte和double轉換
/**
* double轉換byte
*
* @param bb
* @param x
* @param index
*/
public static void putDouble(byte[] bb, double x, int index) {
// byte[] b = new byte[8];
long l = Double.doubleToLongBits(x);
for (int i = 0; i < 4; i++) {
bb[index + i] = new Long(l).byteValue();
l = l >> 8;
}
}
/**
* 通過byte數組取得float
*
* @param bb
* @param index
* @return
*/
public static double getDouble(byte[] b, int index) {
long l;
l = b[0];
l &= 0xff;
l |= ((long) b[1] << 8);
l &= 0xffff;
l |= ((long) b[2] << 16);
l &= 0xffffff;
l |= ((long) b[3] << 24);
l &= 0xffffffffl;
l |= ((long) b[4] << 32);
l &= 0xffffffffffl;
l |= ((long) b[5] << 40);
l &= 0xffffffffffffl;
l |= ((long) b[6] << 48);
l &= 0xffffffffffffffl;
l |= ((long) b[7] << 56);
return Double.longBitsToDouble(l);
}
}
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