public int strStr(String haystack, String needle) {

if (needle == null || needle.length() == 0) return 0;

if (haystack == null || haystack.length() == 0 || haystack.length() < needle.length()) return -1;

int i = 0;

while (i <= haystack.length() - needle.length()) {

int j = 0;

int t = i;

while (j < needle.length() && haystack.charAt(t) == needle.charAt(j)) {

j++;

t++;

}

if (j == needle.length()) return i;

i++;

}

return -1;

}

/**

public int strStr2(String haystack, String needle) {

int l1 = haystack.length(), l2 = needle.length();

if (l1 < l2) {

return -1;

} else if (l2 == 0) {

return 0;

}

int threshold = l1 - l2;

for (int i = 0; i <= threshold; ++i) {

if (haystack.substring(i,i+l2).equals(needle)) {

return i;

}

}

return -1;

}