8009240: RegExpScanner code is inefficient and too complex

Reviewed-by: jlaskey, lagergren

nashorn/src/jdk/nashorn/internal/runtime/regexp/JoniRegExp.java

@@ -117,10 +117,6 @@ public class JoniRegExp extends RegExp {
             return new JoniRegExp(pattern, flags);
         }
 
-        @Override
-        protected String replaceToken(final String str) {
-            return str.equals("[^]") ? "[\\s\\S]" : str;
-        }
     }
 
     class JoniMatcher implements RegExpMatcher {

nashorn/src/jdk/nashorn/internal/runtime/regexp/RegExpFactory.java

@@ -67,25 +67,6 @@ public class RegExpFactory {
         return new DefaultRegExp(pattern, flags);
     }
 
-    /**
-     * Replace a regexp token as suitable for regexp instances created by this factory.
-     *
-     * @param str a regular expression token
-     * @return the replacement token
-     */
-    protected String replaceToken(final String str) {
-        switch (str) {
-            case "\\s":
-                return "[" + Lexer.getWhitespaceRegExp() + "]";
-            case "\\S":
-                return "[^" + Lexer.getWhitespaceRegExp() + "]";
-            case "[^]":
-                return "[\\s\\S]";
-            default:
-                return str;
-        }
-    }
-
     /**
      * Compile a regexp with the given {@code source} and {@code flags}.
      *
@@ -98,16 +79,6 @@ public class RegExpFactory {
         return instance.compile(pattern,  flags);
     }
 
-    /**
-     * Replace a regexp token as needed by the currently installed factory instance.
-     *
-     * @param token a regexp token
-     * @return the replacement token
-     */
-    public static String replace(final String token) {
-        return instance.replaceToken(token);
-    }
-
     /**
      * Validate a regexp with the given {@code source} and {@code flags}.
      *
@@ -120,4 +91,13 @@ public class RegExpFactory {
     public static void validate(final String pattern, final String flags) throws ParserException {
         instance.compile(pattern, flags);
     }
+
+    /**
+     * Returns true if the instance uses the JDK's {@code java.util.regex} package.
+     *
+     * @return true if instance uses JDK regex package
+     */
+    public static boolean usesJavaUtilRegex() {
+        return instance != null && instance.getClass() == RegExpFactory.class;
+    }
 }