[java] BlockJoinLinesHandler: avoid removing block when there's only comment inside (IDEA-264288)

GitOrigin-RevId: dad4d5ffb573d186463589162adbd2fcd610157d

java/java-impl/src/com/intellij/codeInsight/editorActions/BlockJoinLinesHandler.java

@@ -56,7 +56,7 @@ public class BlockJoinLinesHandler implements JoinLinesHandlerDelegate {
       if (foundStatement != null) return -1;
       foundStatement = element;
     }
-    if (foundStatement == null) return -1;
+    if (!(foundStatement instanceof PsiStatement)) return -1;
     PsiElement parent = codeBlock.getParent();
     if (isPotentialShortIf(foundStatement) && parent instanceof PsiBlockStatement) {
       PsiElement grandParent = parent.getParent();

java/java-tests/testData/codeInsight/joinLines/IfBlockWithComment.java

@@ -0,0 +1,9 @@
+class C {
+  private static void fn(boolean cond) {
+    <caret>if (cond) {
+      // comment
+    } else {
+      
+    }
+  }
+}

java/java-tests/testData/codeInsight/joinLines/IfBlockWithComment_after.java

@@ -0,0 +1,8 @@
+class C {
+  private static void fn(boolean cond) {
+    if (cond) {// comment
+    } else {
+      
+    }
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/JoinLinesTest.java

@@ -198,6 +198,7 @@ public class JoinLinesTest extends LightJavaCodeInsightTestCase {
   
   public void testUnwrapCodeBlockIfElse() { doTest(); }
   public void testUnwrapCodeBlockIfElse2() { doTest(); }
+  public void testIfBlockWithComment() { doTest(); }
   public void testAssignmentExpression() { doTest(); }
   public void testAssignmentExpression2() { doTest(); }
   public void testAssignmentExpressionPrecedence() { doTest(); }