Adding analyzer feedback for Squeaky Clean concept exercise

exercises/concept/squeaky-clean/.docs/hints.md

@@ -3,29 +3,24 @@
 ## 1. Replace any spaces encountered with underscores
 
 - [This tutorial][chars-tutorial] is useful.
-- [Reference documentation][chars-docs] for `char`s is here.
 - You can retrieve `char`s from a string using the [charAt][char-at] method.
 - You should use a [`StringBuilder`][string-builder] to build the output string.
-- See [this method][iswhitespace] for detecting spaces. Remember it is a static method.
+- Check the [Character][chars-docs] documentation for a method to detect whitespaces. Remember it is a static method.
 - `char` literals are enclosed in single quotes.
 
 ## 2. Convert kebab-case to camel-case
 
-- See [this method][toupper] to convert a character to upper case.
+- Check the [Character][chars-docs] documentation for a method to convert a character to upper case. Remember it is a static method.
 
 ## 3. Convert leetspeak to normal text
 
-- See [this method][isdigit] for detecting numbers.
+- Check the [Character][chars-docs] documentation for a method to detect when a character is a digit. Remember it is a static method.
 
 ## 4. Omit characters that are not letters
 
-- See [this method][isletter] to check if a character is a letter.
+- Check the [Character][chars-docs] documentation for a method to detect when a character is a letter. Remember it is a static method.
 
 [chars-docs]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/Character.html
 [chars-tutorial]: https://docs.oracle.com/javase/tutorial/java/data/characters.html
 [char-at]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html#charAt(int)
 [string-builder]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/StringBuilder.html
-[iswhitespace]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/Character.html#isWhitespace(char)
-[toupper]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/Character.html#toUpperCase(char)
-[isletter]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/Character.html#isLetter(char)
-[isdigit]: https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/Character.html#isDigit(char)

exercises/concept/squeaky-clean/.meta/design.md

@@ -27,3 +27,18 @@
 
 - `strings`: know of the `string` type that will be iterated over and accessed by index.
 - `for-loop` for loops (rather than foreach) are the best means of highlighting the relationship between strings and `char`s
+
+## Analyzer
+
+This exercise could benefit from the following rules in the [analyzer]:
+
+- `actionable`: If the solution did not use `Character.isWhitespace`, instruct the student to do so, because this concept intends to teach the character concept and methods.
+- `actionable`: If the solution did not use `Character.isDigit`, instruct the student to do so.
+- `actionable`: If the solution did not use `Character.isLetter`, instruct the student to do so.
+- `actionable`: If the solution did not use `Character.toUpperCase`, instruct the student to do so.
+- `informative`: If the solution uses string concatenation instead of `StringBuilder`, inform the student that this cause a small performance and memory penalty compared to `StringBuilder`.
+
+If the solution does not receive any of the above feedback, it must be exemplar.
+Leave a `celebratory` comment to celebrate the success!
+
+[analyzer]: https://github.com/exercism/java-analyzer

exercises/concept/squeaky-clean/.meta/src/reference/java/SqueakyClean.java

@@ -24,7 +24,7 @@ static String clean(String identifier) {
         boolean kebab = false;
         for (int i = 0; i < identifier.length(); i++) {
             final char ch = identifier.charAt(i);
-            if (Character.isSpaceChar(ch)) {
+            if (Character.isWhitespace(ch)) {
                 cleanIdentifier.append("_");
             } else if (Character.isDigit(ch)) {
                 cleanIdentifier.append(SqueakyClean.replaceDigit(ch));