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/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.bson.util;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ConcurrentMap;

import static java.util.Collections.unmodifiableList;

@SuppressWarnings("deprecation")
class ClassAncestry {

    /**
     * 

Walks superclass and interface graph, superclasses first, then interfaces, to compute an ancestry list. Supertypes are visited * left * to right. Duplicates are removed such that no Class will appear in the list before one of its subtypes.

* *

Does not need to be synchronized, races are harmless as the Class graph does not change at runtime.

*/ public static List> getAncestry(final Class c) { ConcurrentMap, List>> cache = getClassAncestryCache(); while (true) { List> cachedResult = cache.get(c); if (cachedResult != null) { return cachedResult; } cache.putIfAbsent(c, computeAncestry(c)); } } /** * Starting with children and going back to parents */ private static List> computeAncestry(final Class c) { List> result = new ArrayList>(); result.add(Object.class); computeAncestry(c, result); Collections.reverse(result); return unmodifiableList(new ArrayList>(result)); } private static void computeAncestry(final Class c, final List> result) { if ((c == null) || (c == Object.class)) { return; } // first interfaces (looks backwards but is not) Class[] interfaces = c.getInterfaces(); for (int i = interfaces.length - 1; i >= 0; i--) { computeAncestry(interfaces[i], result); } // next superclass computeAncestry(c.getSuperclass(), result); if (!result.contains(c)) { result.add(c); } } /** * classAncestryCache */ private static ConcurrentMap, List>> getClassAncestryCache() { return (_ancestryCache); } private static final ConcurrentMap, List>> _ancestryCache = CopyOnWriteMap.newHashMap(); }




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