[java] UnnecessaryFullyQualifiedName - add test for #4133

Fixes #4133

docs/pages/release_notes.md

@@ -48,6 +48,7 @@ from Lua. This means, that the Lua language in PMD can now parse both Lua and Lu
 * java-codestyle
     * [#3859](https://github.com/pmd/pmd/issues/3859): \[java] CommentDefaultAccessModifier is triggered in JUnit5 test class
     * [#4085](https://github.com/pmd/pmd/issues/4085): \[java] UnnecessaryFullyQualifiedName false positive when nested and non-nested classes with the same name and in the same package are used together
+    * [#4133](https://github.com/pmd/pmd/issues/4133): \[java] UnnecessaryFullyQualifiedName - FP for inner class pkg.ClassA.Foo implementing pkg.Foo
 * java-design
     * [#4090](https://github.com/pmd/pmd/issues/4090): \[java] FinalFieldCouldBeStatic false positive with non-static synchronized block (regression in 6.48, worked with 6.47)
 * java-errorprone

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/codestyle/unnecessaryfullyqualifiedname/ClassA.java

@@ -0,0 +1,14 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.java.rule.codestyle.unnecessaryfullyqualifiedname;
+
+/**
+ * Test case for #4133
+ */
+public class ClassA {
+    public static class Foo implements net.sourceforge.pmd.lang.java.rule.codestyle.unnecessaryfullyqualifiedname.Foo {
+
+    }
+}

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/rule/codestyle/unnecessaryfullyqualifiedname/Foo.java

@@ -0,0 +1,8 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.java.rule.codestyle.unnecessaryfullyqualifiedname;
+
+public interface Foo {
+}

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/rule/codestyle/xml/UnnecessaryFullyQualifiedName.xml

@@ -718,4 +718,16 @@ public class SomeClass {
 }
         ]]></code>
     </test-code>
+    
+    <test-code>
+        <description>[java] UnnecessaryFullyQualifiedName - FP for inner class pkg.ClassA.Foo implementing pkg.Foo #4133</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+package net.sourceforge.pmd.lang.java.rule.codestyle.unnecessaryfullyqualifiedname;
+
+public class ClassA {
+    public static class Foo implements net.sourceforge.pmd.lang.java.rule.codestyle.unnecessaryfullyqualifiedname.Foo {}
+}
+]]></code>
+    </test-code>
 </test-data>