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8296287: Improve documentation for Types.directSupertypes()
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Reviewed-by: jlahoda, prappo
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jddarcy committed Nov 4, 2022
1 parent f9c7cda commit 97c5a64
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,10 @@ public interface Types {
* will appear last in the list. For an interface type with no direct
* super-interfaces, a type mirror representing {@code java.lang.Object}
* is returned.
* The type {@code java.lang.Object} has no direct supertype (JLS
* {@jls 8.1.4}, {@jls 8.1.5}) so an empty list is returned for
* the direct supertypes of a type mirror representing {@code
* java.lang.Object}.
* @param t the type being examined
* @return the direct supertypes, or an empty list if none
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Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
* Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit if you need additional information or have any
* questions.

* @test
* @bug 8296287
* @summary Test direct supertypes of java.lang.Object
* @library /tools/javac/lib
* @build JavacTestingAbstractProcessor TestDirectSupertypeObject
* @compile -processor TestDirectSupertypeObject -proc:only

import java.util.*;
import javax.annotation.processing.*;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Types;
import static java.util.Objects.*;

* Verify java.lang.Object has an empty list of direct supertypes.
public class TestDirectSupertypeObject extends JavacTestingAbstractProcessor {
public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
if (!roundEnv.processingOver()) {
TypeMirror objectType = requireNonNull(eltUtils.getTypeElement("java.lang.Object")).asType();
var objectSupertypes = typeUtils.directSupertypes(objectType);
if (!objectSupertypes.isEmpty()) {
messager.printError("Direct supertypes: " + objectSupertypes);
return true;

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