create rspec for rule "Don't test if the variable is null before a sw…

…itch"

rules/S6888/java/metadata.json

@@ -1,24 +1,23 @@
 {
-  "title": "FIXME",
+  "title": "Don't test if the variable is null before a switch",
   "type": "CODE_SMELL",
   "status": "ready",
   "remediation": {
     "func": "Constant\/Issue",
     "constantCost": "5min"
   },
   "tags": [
+    "java21"
   ],
-  "defaultSeverity": "Major",
+  "defaultSeverity": "MEDIUM",
   "ruleSpecification": "RSPEC-6888",
   "sqKey": "S6888",
   "scope": "All",
   "defaultQualityProfiles": ["Sonar way"],
   "quickfix": "unknown",
   "code": {
     "impacts": {
-      "MAINTAINABILITY": "HIGH",
-      "RELIABILITY": "MEDIUM",
-      "SECURITY": "LOW"
+      "MAINTAINABILITY": "MEDIUM"
     },
     "attribute": "CONVENTIONAL"
   }

rules/S6888/java/rule.adoc

@@ -1,44 +1,47 @@
-FIXME: add a description
+Don't test if the variable is null before a switch
 
-// If you want to factorize the description uncomment the following line and create the file.
-//include::../description.adoc[]
 
 == Why is this an issue?
 
-FIXME: remove the unused optional headers (that are commented out)
+Since Java 21, can accept null values. Thus, it not necessary anymore to check if a variable is null before matching it and should even be avoided, as it lead to less readable code.
 
-//=== What is the potential impact?
 
 == How to fix it
-//== How to fix it in FRAMEWORK NAME
+
+Move the null check inside the switch statement.
 
 === Code examples
 
 ==== Noncompliant code example
 
-[source,text,diff-id=1,diff-type=noncompliant]
+[source,java,diff-id=1,diff-type=noncompliant]
 ----
-FIXME
+static void f(String s) {
+  if (s == null) { // Noncompliant, we can move the null check in the switch statement.
+    System.out.println("Oops!");
+    return;
+  }
+  switch (s) {
+    case "Foo", "Bar" -> System.out.println("Great");
+    default           -> System.out.println("Ok");
+   }
+}
 ----
 
 ==== Compliant solution
 
-[source,text,diff-id=1,diff-type=compliant]
+[source,java,diff-id=1,diff-type=compliant]
 ----
-FIXME
+static void f(String s) {
+  switch (s) {
+    case null         -> System.out.println("Oops!");
+    case "Foo", "Bar" -> System.out.println("Great");
+    default           -> System.out.println("Ok");
+   }
+}
 ----
 
-//=== How does this work?
-
-//=== Pitfalls
-
-//=== Going the extra mile
 
 
-//== Resources
-//=== Documentation
-//=== Articles & blog posts
-//=== Conference presentations
-//=== Standards
-//=== External coding guidelines
-//=== Benchmarks
+== Resources
+* https://openjdk.org/jeps/441[Pattern Matching for Switch]