Exam 5. Bit Flipper (on Java code)

import java.math.BigInteger;
import java.util.Scanner;

public class _5_BitFlipper {

    private static final BigInteger SEVEN = new BigInteger("7");

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner scan = new Scanner(System.in);
        BigInteger number = scan.nextBigInteger();

        BigInteger bitMask;
        BigInteger bitValue;
        for (int position = 63; position >= 2; position--) {
            bitMask = SEVEN.shiftLeft(position - 2);
            bitValue = number.and(bitMask);
            bitValue = bitValue.shiftRight(position - 2);
            if (bitValue.equals(BigInteger.ZERO)) {
                number = number.or(bitMask);
                position -= 2;
            } else if (bitValue.equals(SEVEN)) {
                number = number.andNot(bitMask);
                position -= 2;
            }
        }

        System.out.println(number);
    }

}