ExtractMethodProcessor: fix NPE extracting method from empty parenthesis: EA-214509

GitOrigin-RevId: 5fc2d19d08efca879d6e8174d0a8500eb7803dc5

java/java-impl/src/com/intellij/refactoring/extractMethod/ExtractMethodProcessor.java

@@ -143,8 +143,13 @@ public class ExtractMethodProcessor implements MatchProvider {
     myProject = project;
     myEditor = editor;
     if (elements.length != 1 || !(elements[0] instanceof PsiBlockStatement)) {
-      myElements = elements.length == 1 && elements[0] instanceof PsiParenthesizedExpression
-                   ? new PsiElement[] {PsiUtil.skipParenthesizedExprDown((PsiExpression)elements[0])} : elements;
+      if (elements.length == 1 && elements[0] instanceof PsiParenthesizedExpression) {
+        PsiExpression expression = PsiUtil.skipParenthesizedExprDown((PsiExpression)elements[0]);
+        myElements = expression != null ? new PsiElement[]{expression} : elements;
+      }
+      else {
+        myElements = elements;
+      }
       myEnclosingBlockStatement = null;
     }
     else {

java/java-tests/testData/refactoring/extractMethod/EmptyParenthesis.java

@@ -0,0 +1,6 @@
+
+class C {
+    void foo() {
+        int x = <selection>()</selection>;
+    }
+}

java/java-tests/testSrc/com/intellij/java/refactoring/ExtractMethodTest.java

@@ -1170,6 +1170,15 @@ public class ExtractMethodTest extends LightJavaCodeInsightTestCase {
     doTest();
   }
 
+  public void testEmptyParenthesis() throws Exception {
+    try {
+      doTest();
+      fail("Should not work for empty parenthesis");
+    }
+    catch (PrepareFailedException ignore) {
+    }
+  }
+
   public void testQualifyWhenConflictingNamePresent() throws Exception {
     final CommonCodeStyleSettings settings = CodeStyleSettingsManager.getSettings(getProject()).getCommonSettings(JavaLanguage.INSTANCE);
     settings.ELSE_ON_NEW_LINE = true;