Gray Code or Binary numeral system in Java

The gray code is a binary numeral system where two successive values differ in only one bit. Given a non-negative integer n representing the total number of bits in the code, print the sequence of gray code. A gray code sequence must begin with 0.

For example, given n = 2, return [0,1,3,2]. Its gray code sequence is: 00 – 0 01 – 1 11 – 3 10 – 2.

The solution in Java:

package com.algorithm.graycode;

import java.util.ArrayList;
import java.util.List;

public class BinaryCodeSystem {

    public static void main(String[] args) {
        grayCode(2).forEach(i->System.out.println(i));
    }

    public static List<Integer> grayCode(int n) {
        if (n == 0) {
            List<Integer> result = new ArrayList<Integer>();
            result.add(0);
            return result;
        }
        List<Integer> result = grayCode(n - 1);
        int numToAdd = 1 << (n - 1);
        for (int i = result.size() - 1; i >= 0; i--) {
            result.add(numToAdd + result.get(i));
        }
        return result;
    }
}

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