/**

* Implement strStr().

*

* Returns a pointer to the first occurrence of needle in haystack, or null if

* needle is not part of haystack.

*/

public class ImplementStrStr {

public String strStr(String haystack, String needle) {

int i = 0;

int len1 = haystack.length();

int len2 = needle.length();

if (len1 == 0 && len2 == 0)

return "";

for (; i < len1; i++) {

int a = i;

int b = 0;

boolean match = true;

while (b < len2) {

if (a >= len1 || haystack.charAt(a) != needle.charAt(b)) {

match = false;

break;

} else {

a++;

b++;

}

}

if (match)

return haystack.substring(i);

}

return null;

}

}