obsolete class!
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/*
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* Copyright (C) 2011 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson;
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import java.lang.reflect.Constructor;
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/**
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* Use the default constructor on the class to instantiate an object.
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*
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* @author Joel Leitch
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*/
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final class DefaultConstructorAllocator {
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private static final Constructor<Null> NULL_CONSTRUCTOR = createNullConstructor();
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private final Cache<Class<?>, Constructor<?>> constructorCache;
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public DefaultConstructorAllocator() {
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this(200);
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}
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public DefaultConstructorAllocator(int cacheSize) {
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constructorCache = new LruCache<Class<?>, Constructor<?>>(cacheSize);
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}
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// for testing purpose
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final boolean isInCache(Class<?> cacheKey) {
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return constructorCache.getElement(cacheKey) != null;
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}
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private static final Constructor<Null> createNullConstructor() {
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try {
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return getNoArgsConstructor(Null.class);
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} catch (Exception e) {
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return null;
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}
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}
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public <T> T newInstance(Class<T> c) throws Exception {
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Constructor<T> constructor = findConstructor(c);
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return (constructor != null) ? constructor.newInstance() : null;
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}
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@SuppressWarnings("unchecked")
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private <T> Constructor<T> findConstructor(Class<T> c) {
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Constructor<T> cachedElement = (Constructor<T>) constructorCache.getElement(c);
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if (cachedElement != null) {
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if (cachedElement == NULL_CONSTRUCTOR) {
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return null;
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} else {
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return cachedElement;
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}
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}
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Constructor<T> noArgsConstructor = getNoArgsConstructor(c);
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if (noArgsConstructor != null) {
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constructorCache.addElement(c, noArgsConstructor);
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} else {
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constructorCache.addElement(c, NULL_CONSTRUCTOR);
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}
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return noArgsConstructor;
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}
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private static <T> Constructor<T> getNoArgsConstructor(Class<T> c) {
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try {
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Constructor<T> declaredConstructor = c.getDeclaredConstructor();
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declaredConstructor.setAccessible(true);
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return declaredConstructor;
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} catch (Exception e) {
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return null;
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}
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}
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// placeholder class for Null constructor
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private static final class Null {
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}
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}
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