e8efcd82a8
Motivation: We can just use Objects.requireNonNull(...) as a replacement for ObjectUtil.checkNotNull(....) Modifications: - Use Objects.requireNonNull(...) Result: Less code to maintain.
129 lines
4.0 KiB
Java
129 lines
4.0 KiB
Java
/*
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* Copyright 2013 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. 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, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.util;
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import static java.util.Objects.requireNonNull;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.atomic.AtomicInteger;
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/**
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* A pool of {@link Constant}s.
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*
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* @param <T> the type of the constant
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*/
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public abstract class ConstantPool<T extends Constant<T>> {
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private final ConcurrentMap<String, T> constants = new ConcurrentHashMap<>();
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private final AtomicInteger nextId = new AtomicInteger(1);
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/**
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* Shortcut of {@link #valueOf(String) valueOf(firstNameComponent.getName() + "#" + secondNameComponent)}.
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*/
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public T valueOf(Class<?> firstNameComponent, String secondNameComponent) {
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requireNonNull(firstNameComponent, "firstNameComponent");
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requireNonNull(secondNameComponent, "secondNameComponent");
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return valueOf(firstNameComponent.getName() + '#' + secondNameComponent);
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}
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/**
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* Returns the {@link Constant} which is assigned to the specified {@code name}.
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* If there's no such {@link Constant}, a new one will be created and returned.
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* Once created, the subsequent calls with the same {@code name} will always return the previously created one
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* (i.e. singleton.)
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*
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* @param name the name of the {@link Constant}
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*/
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public T valueOf(String name) {
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checkNotNullAndNotEmpty(name);
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return getOrCreate(name);
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}
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/**
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* Get existing constant by name or creates new one if not exists. Threadsafe
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*
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* @param name the name of the {@link Constant}
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*/
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private T getOrCreate(String name) {
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T constant = constants.get(name);
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if (constant == null) {
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final T tempConstant = newConstant(nextId(), name);
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constant = constants.putIfAbsent(name, tempConstant);
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if (constant == null) {
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return tempConstant;
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}
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}
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return constant;
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}
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/**
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* Returns {@code true} if a {@link AttributeKey} exists for the given {@code name}.
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*/
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public boolean exists(String name) {
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checkNotNullAndNotEmpty(name);
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return constants.containsKey(name);
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}
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/**
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* Creates a new {@link Constant} for the given {@code name} or fail with an
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* {@link IllegalArgumentException} if a {@link Constant} for the given {@code name} exists.
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*/
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public T newInstance(String name) {
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checkNotNullAndNotEmpty(name);
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return createOrThrow(name);
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}
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/**
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* Creates constant by name or throws exception. Threadsafe
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*
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* @param name the name of the {@link Constant}
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*/
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private T createOrThrow(String name) {
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T constant = constants.get(name);
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if (constant == null) {
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final T tempConstant = newConstant(nextId(), name);
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constant = constants.putIfAbsent(name, tempConstant);
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if (constant == null) {
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return tempConstant;
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}
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}
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throw new IllegalArgumentException(String.format("'%s' is already in use", name));
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}
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private static String checkNotNullAndNotEmpty(String name) {
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requireNonNull(name, "name");
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if (name.isEmpty()) {
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throw new IllegalArgumentException("empty name");
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}
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return name;
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}
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protected abstract T newConstant(int id, String name);
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@Deprecated
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public final int nextId() {
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return nextId.getAndIncrement();
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}
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}
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