8308753: Class-File API transition to Preview

Reviewed-by: ihse, mchung, vromero

src/java.base/share/classes/java/lang/classfile/CompoundElement.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.lang.classfile;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+import jdk.internal.javac.PreviewFeature;
+
+/**
+ * A {@link ClassFileElement} that has complex structure defined in terms of
+ * other classfile elements, such as a method, field, method body, or entire
+ * class.  When encountering a {@linkplain CompoundElement}, clients have the
+ * option to treat the element as a single entity (e.g., an entire method)
+ * or to traverse the contents of that element with the methods in this class
+ * (e.g., {@link #elements()}, {@link #forEachElement(Consumer)}, etc.)
+ * @param <E> the element type
+ *
+ * @sealedGraph
+ * @since 22
+ */
+@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
+public sealed interface CompoundElement<E extends ClassFileElement>
+        extends ClassFileElement, Iterable<E>
+        permits ClassModel, CodeModel, FieldModel, MethodModel, jdk.internal.classfile.impl.AbstractUnboundModel {
+    /**
+     * Invoke the provided handler with each element contained in this
+     * compound element
+     * @param consumer the handler
+     */
+    void forEachElement(Consumer<E> consumer);
+
+    /**
+     * {@return an {@link Iterable} describing all the elements contained in this
+     * compound element}
+     */
+    default Iterable<E> elements() {
+        return elementList();
+    }
+
+    /**
+     * {@return an {@link Iterator} describing all the elements contained in this
+     * compound element}
+     */
+    @Override
+    default Iterator<E> iterator() {
+        return elements().iterator();
+    }
+
+    /**
+     * {@return a {@link Stream} containing all the elements contained in this
+     * compound element}
+     */
+    default Stream<E> elementStream() {
+        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
+                                            iterator(),
+                                            Spliterator.IMMUTABLE | Spliterator.NONNULL | Spliterator.ORDERED),
+                                    false);
+    }
+
+    /**
+     * {@return an {@link List} containing all the elements contained in this
+     * compound element}
+     */
+    default List<E> elementList() {
+        List<E> list = new ArrayList<>();
+        forEachElement(new Consumer<>() {
+            @Override
+            public void accept(E e) {
+                list.add(e);
+            }
+        });
+        return list;
+    }
+
+}