LeetCode - PlusOne

public class Solution {
    public int[] plusOne(int[] digits) {
	    java.math.BigInteger Bigdigits = new java.math.BigInteger(toString(digits));
		String s = Bigdigits.add(new java.math.BigInteger("1")).toString();
		return toArray(s);
	}
	public static String toString(int[] d) {
		StringBuilder sb = new StringBuilder();
		for(int i=0; i<d.length; i++) {
			sb.append(d[i]);
		}
		return sb.toString();
	}
	public static int[] toArray(String s) {
		int[] ans = new int[s.length()];
		for(int i=0; i<s.length(); i++) {
			ans[i] = s.charAt(i) - ‘0‘;
		}
		return ans;
	}
}