'''

```
int h = haystack.length();
int n = needle.length();
if(n==0&&h==0|| h!=0&&n==0 ) return 0;
if(n>h || h==0 ) return -1;
for(int i=0;i<h-n+1;i++)
{
if(haystack.charAt(i)==needle.charAt(0))
{
if(haystack.substring(i, n+i).equalsIgnoreCase(needle))
return i;
}
}
return -1;
```

'''