String equality check by only reference

As we know if we do a check like below the output will be equal.

String s1 = "stackoverflow";
String s2 = "stackoverflow";
if(s1==s2){
    System.out.println("equal");
}

So my question is if i am not using new operator in my application to create String and all are strings are literals so can i use only reference equality as given above? Thanks in advance.

N.B: i am writing a crawler so i need to check whether i have already visited the given url that i am currently holding. I am using murmur hash which gives me a long for every url but there are collision so i need to check for the content if the url string if there is a hash collision. Hence for performance i am thinking of just comparing the reference equality of two string urls. And i am using jsoup for html parsing.