java int to byte and long to byte

In network programming, due to the need to save bandwidth or encoding, it is usually necessary to process long and int natively instead of converting to string.

public class ByteOrderUtils {
public static byte[] int2byte(int res) { 
byte[] targets = new byte[4]; 
targets[3] = (byte) (res & 0xff);// 最低位 
targets[2] = (byte) ((res >> 8) & 0xff);// 次低位 
targets[1] = (byte) ((res >> 16) & 0xff);// 次高位 
targets[0] = (byte) (res >>> 24);// 最高位,无符号右移。 
return targets; 
}
public static int byteArrayToInt(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; 
}
public static byte[] long2byte(long res) { 
byte[] buffer = new byte[8]; 
for (int i = 0; i < 8; i++) { 
int offset = 64 - (i + 1) * 8; 
buffer[i] = (byte) ((res >> offset) & 0xff); 
}
return buffer;
}
public static long byteArrayToLong(byte[] b){ 
long values = 0; 
for (int i = 0; i < 8; i++) { 
values <<= 8; values|= (b[i] & 0xff); 
} 
return values; 
}
}