SONARJAVA-5517 Modify S1481: add information about the java unnamed pattern

rules/S1481/java/metadata.json

@@ -1,3 +1,6 @@
 {
-  "quickfix": "partial"
+  "quickfix": "partial",
+  "tags": [
+    "java22", "unused"
+  ]
 }

rules/S1481/java/rule.adoc

@@ -1,6 +1,10 @@
 include::../rationale.adoc[]
 
-include::../how-to-fix-it.adoc[]
+== How to fix it
+
+The fix for this issue is straightforward. Once you ensure the unused variable is not part of an incomplete implementation, you just need to remove it.
+
+Java 22 introduces the unnamed variable pattern ``++_++``. When a variable declared within a pattern match, an enhanced for loop, or a try with resource is unused, you should replace its name with the unnamed variable pattern to clearly indicate the intent not to use the variable.
 
 === Code examples
 
@@ -9,10 +13,55 @@ include::../how-to-fix-it.adoc[]
 [source,java,diff-id=1,diff-type=noncompliant]
 ----
 public int numberOfMinutes(int hours) {
-  int seconds = 0;   // Noncompliant - seconds is unused 
+  int seconds = 0;   // Noncompliant: "seconds" is unused
   return hours * 60;
 }
 ----
+[source,java,diff-id=2,diff-type=noncompliant]
+----
+public String name(Person p) {
+  return switch(p){
+    case User(String name, int age) -> name; // Noncompliant: "age" is unused replace it with the unnamed variable pattern (starting from Java 22)
+    default -> throw new IllegalArgumentException();
+  };
+}
+----
+[source,java,diff-id=3,diff-type=noncompliant]
+----
+public String type(Person p) {
+    return switch (p) {
+      case User user -> "user"; // Noncompliant:  "user" is unused replace it with the unnamed variable pattern (starting from Java 22)
+      default -> throw new IllegalArgumentException();
+    };
+}
+----
+[source,java,diff-id=4,diff-type=noncompliant]
+----
+public int age(Person p) {
+    if (p instanceof User(String name, int age)) { // Noncompliant:  "name" is unused replace it with the unnamed variable pattern (starting from Java 22)
+      return age;
+    }
+}
+----
+[source,java,diff-id=5,diff-type=noncompliant]
+----
+public static int count(int[] elements) {
+    int count = 0;
+    for (var el : elements) { // Noncompliant:  "el" is unused replace it with the unnamed variable pattern (starting from Java 22)
+      count++;
+    }
+    return count;
+}
+----
+[source,java,diff-id=6,diff-type=noncompliant]
+----
+public void foo() {
+    try (var file = Files.createTempFile(directory, "temp", ".txt")) { // Noncompliant:  "file" is unused replace it with the unnamed variable pattern (starting from Java 22)
+      System.out.println("file created");
+    }
+}
+----
+
 
 ==== Compliant solution
 
@@ -22,6 +71,50 @@ public int numberOfMinutes(int hours) {
   return hours * 60;
 }
 ----
+[source,java,diff-id=2,diff-type=compliant]
+----
+public String name(Person p) {
+    return switch (p) {
+      case User(String name, _) -> name; // Compliant
+      default -> throw new IllegalArgumentException();
+    };
+}
+----
+[source,java,diff-id=3,diff-type=compliant]
+----
+public String type(Person p) {
+    return switch (p) {
+      case User _ -> "user"; // Compliant
+      default -> throw new IllegalArgumentException();
+    };
+}
+----
+[source,java,diff-id=4,diff-type=compliant]
+----
+public int age(Person p) {
+    if(p instanceof User(String _, int age)) { // Compliant
+      return age;
+    }
+}
+----
+[source,java,diff-id=5,diff-type=compliant]
+----
+public static int count(int[] elements) {
+    int count = 0;
+    for (var _ : elements) { // Compliant
+      count++;
+    }
+    return count;
+}
+----
+[source,java,diff-id=6,diff-type=compliant]
+----
+ public void foo() {
+    try (var _ = Files.createTempFile(directory, "temp", ".txt")) { // Compliant
+      System.out.println("file created");
+    }
+}
+----
 
 ifdef::env-github,rspecator-view[]