55 lines
1.5 KiB
Java
55 lines
1.5 KiB
Java
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/*
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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 java.util.HashMap;
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import java.util.Map;
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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 Map<String, T> constants = new HashMap<String, T>();
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private int nextId = 1;
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/**
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* Creates a new or the existing {@link Constant} mapped to the specified {@code name}.
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*/
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public T valueOf(String name) {
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if (name == null) {
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throw new NullPointerException("name");
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}
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synchronized (constants) {
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T c = constants.get(name);
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if (c == null) {
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c = newConstant(nextId, name);
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constants.put(name, c);
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nextId ++;
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}
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return c;
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}
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}
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protected abstract T newConstant(int id, String name);
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}
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