Convert an UNSIGNED byte to a JAVA type
In JAVA, a byte always considered as signed when converted to another type. We must mask the sign bit to JAVA, cast to an integer and process the masked bit if needed. The following method implements this idea :

public class UnsignedByte {

    public static void main (String args[]) {

        byte b1 = 127;

        byte b2 = -128;

        byte b3 = -1;        System.out.println(b1); //127

        System.out.println(b2); //-128

        System.out.println(b3); //-1

        System.out.println(unsignedByteToInt(b1)); //127

        System.out.println(unsignedByteToInt(b2)); //128

        System.out.println(unsignedByteToInt(b3)); //255

   }

   public static int unsignedByteToInt(byte b) {

        return (int) b & 0xFF;

   }

}

Therefore for an array of 4 bytes (buf[]), which represents an integer :
int i = 0;

int pos = 0;

i += unsignedByteToInt(buf[pos++]) << 24;

i += unsignedByteToInt(buf[pos++]) << 16;

i += unsignedByteToInt(buf[pos++]) << 8;

i += unsignedByteToInt(buf[pos++]) << 0;To convert a byte to it's hexadecimal equivalent

public static String byteToHex(byte b){

    int i = b & 0xFF;

    return Integer.toHexString(i);

}
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