Using Scanner in Java how can I hasNext(aString) where the string is not regex pattern?

Question

Hi, I am trying to do as my question states, sooo I have the following code which would find the match.

String test = scan.next();
if (test.equals("$let"))
return 1;

However, I would prefer to use hasNext as to not consume a token; however, when i do the following it fails.
if (scan.hasNext("$let"))
return 1;

I realize the when giving has next a variable it expects a pattern, but I thought if i don't have any regex symbols it should work. I also thought $ was possibly some regex symbol so I tried /$ however, that did not work!

Thanks for the help!

Answer 1

You should use \\$ to escape the regex, but it's easier to just get the next() and save the result.

Answer 2

In general, if you have some arbitrary string that you want to match literally with no meanings to any regex metacharacters, you can use java.util.Pattern.quote.

Scanner sc = new Scanner("$)}**");
System.out.println(sc.hasNext(Pattern.quote("$)}**"))); // prints "true"
System.out.println(sc.hasNext("\\Q$)}**\\E")); // prints "true"
System.out.println(sc.hasNext("$)}**")); // throws PatternSyntaxException

You can also use the \Q and \E quotation markers, but of course you need to ensure that the quoted string must not itself contain \E.