public class ImplementStrstr {

 public static void main(String[] args) {
 System.out.println(strStr2("qweasdfa", "sdf"));
 }

 public static int strStr(String haystack, String needle) {
 return haystack.indexOf(needle);
 }

 public static int strStr2(String haystack, String needle) {
 int nLength = needle.length();
 if (nLength == 0) {
 return 0;
 }
 for(int left=0, right=nLength-1;right < haystack.length();left++, right++) {
 int i=left;
 for (int nIndex=0;i <= right;i++,nIndex++) {
 if (haystack.charAt(i) != needle.charAt(nIndex)) {
 break;
 }
 }
 if (i==right+1) return left;
 }
 return -1;
 }
}