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java中byte与 int、short、char、float、double之间的转换

由于java的字节序和网络字节序一致(高位在前),给出换算方法,亲测OK
public static void main(String[] args) {
byte[] bs=new byte[2];
short dvalue=1;
Utils.putShort(bs, dvalue, 0);
for (int i = 0; i < bs.length; i++) {
System.out.println(bs[i]);
}
}
/**
* 将32位的int值放到4字节的里
*
* @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下标
result[1] = (byte) (num >>> 16);// 取次高8为放到1下标
result[2] = (byte) (num >>> 8); // 取次低8位放到2下标
result[3] = (byte) (num); // 取最低8位放到3下标
return result;
}

/**
* 将4字节的byte数组转成一个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–) {// 从b的尾部(即int值的低位)开始copy数据
if (j >= 0)
a[i] = b[j];
else
a[i] = 0;// 如果b.length不足4,则将高位补0
}
int v0 = (a[0] & 0xff) << 24;// &0xff将byte值无差异转成int,避免Java自动类型提升后,会保留高位的符号位
int v1 = (a[1] & 0xff) << 16;
int v2 = (a[2] & 0xff) << 8;
int v3 = (a[3] & 0xff);
return v0 + v1 + v2 + v3;
}

/**
* 转换short为byte
*
* @param b
* @param s
* 需要转换的short
* @param index
*/
public static void putShort(byte b[], short s, int index) {
b[index + 0] = (byte) (s >> 8);
b[index + 1] = (byte) (s >> 0);
}

/**
* 通过byte数组取到short
*
* @param b
* @param index
* 第几位开始取
* @return
*/
public static short getShort(byte[] b, int index) {
return (short) (((b[index + 1] << 8) | b[index + 0] & 0xff));
}

/**
* 字符到字节转换
*
* @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++) {
// 将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
}
}

/**
* 字节到字符转换
*
* @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;
}

/**
* float转换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;
}
}

/**
* 通过byte数组取得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);
}

/**
* double转换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;
}
}

/**
* 通过byte数组取得double
*
* @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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