How to convert signed byte array to ascii in Java

It seems that the order of bytes in the result is reverse to that of the array, so you should iterate the array in the reverse order and add each element with a shift by the predefined number of bits:

private static String convertToHexFullByte(byte[] arr) {
    return convertToHex(arr, 8);
}
    
private static String convertToHexHalfByte(byte[] arr) {
    return convertToHex(arr, 4);
}
    
private static String convertToHex(byte[] arr, int bits) {
    long mask = 0;
    for (int i = 0; i < bits; i++) {
        mask |= 1 << i;
    }
    long res = 0;
    for (int i = arr.length - 1, j = 0; i >= 0; i--, j += bits) {
        res |= (arr[i] & mask) << j;
    }

    return Long.toHexString(res).toUpperCase();        
}

Test

public static void main(String args[]) {
    byte[] arr4 = {49, 55, 48, 51, 55};
        
    System.out.println(convertToHexHalfByte(arr4));
        
    byte[] arr8 = {-112, 21, 64, 0, 7, 50, 54, 127};
        
    System.out.println(convertToHexFullByte(arr8));
}

output

17037
901540000732367F