Implement strStr()

Implement strStr().
Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Java

public class Solution {
    public int strStr(String haystack, String needle) {
        if(needle.length() == 0) {
            return 0;
        } else if(haystack.length() < 1) {
            return -1;
        } else if(haystack.length() < needle.length()) {
            return -1;
        }

        int hLength = haystack.length(), nLength = needle.length();

        for(int i = 0; i <= hLength - nLength; i++) {
            for(int j = 0, k = i; j < needle.length(); j++, k++) {
                if(haystack.charAt(k) != needle.charAt(j)) {
                    break;
                } else if(j == needle.length()- 1){
                    return i;
                }
            }
        }
        return -1;
    }
}