Largest Number @LeetCode

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

	import java.util.Arrays;
	import java.util.Comparator;
	/*
	* Integer Camparation is complicated, Transfer to string, connect s1+s2 and s2+s1.
	*/
	public class LargestNumber {
	// For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.
	public static String largestNumber(int[] num) {
	if (num == null || num.length == 0) {
	return "";
	}
	String[] array = new String[num.length];
	for (int i = 0; i < num.length; i++) {
	array[i] = String.valueOf(num[i]);
	}
	Arrays.sort(array, comparator);
	String result = "";
	for (String str: array) {
	result = str + result;
	}
	int i = 0;
	while (i < result.length() - 1) {
	if (result.charAt(i) != '0') {
	break;
	}
	i++;
	}
	return result.substring(i);
	}
	public static Comparator<String> comparator = new Comparator<String>() {
	@Override
	public int compare(String o1, String o2) {
	String comb1 = o1 + o2;
	String comb2 = o2 + o1;
	return comb1.compareTo(comb2);
	}
	};
	public static void main(String[] args) {
	int[] num = {0, 0};
	System.out.println(largestNumber(num));
	}
	}

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