Java - byte[]与int的互相转换

public static int byte2Int(byte[] b, int begin, int len) {
    int sum = 0;
    int end = begin + len;
    int n;
    for (int i = begin; i < end; i++) {
        n = ((int) b[i]) & 0xff;
        n <<= (--len) * 8;
        sum = n + sum;
    }
    return sum;
}
public static byte[] int2byte(int val, int len) {
    byte[] b = new byte[len];
    for (int i = 0; i < len; i++) {
        b[len - i - 1] = (byte) ((val >> 8 * i) & 0xff);
    }
    return b;
}