没看懂的代码：byte[]与int互转

public static int bytes2int(byte[] b) {
int mask = 0xff;
int temp = 0;
int res = 0;
for (int i = 0; i < 4; i++) {
res <<= 8;
temp = b[i] & mask;
res |= temp;
}
return res;
}

public static byte[] int2bytes(int num) {
byte[] b = new byte[4];
for (int i = 0; i < 4; i++) {
b[i] = (byte) (num >>> (24 - i * 8));
}
return b;
}

}