89 lines
2.4 KiB
Java
89 lines
2.4 KiB
Java
/*
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* Copyright (C) 2008 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 org.mcteam.factions.gson;
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import org.mcteam.factions.gson.internal.$Gson$Preconditions;
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import java.util.Stack;
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/**
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* A stack data structure that only does a memory reference comparison
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* when looking for a particular item in the stack. This stack does
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* not allow {@code null} values to be added.
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*
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* @author Joel Leitch
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*/
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final class MemoryRefStack {
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private final Stack<ObjectTypePair> stack = new Stack<ObjectTypePair>();
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/**
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* Adds a new element to the top of the stack.
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*
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* @param obj the object to add to the stack
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* @return the object that was added
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*/
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public ObjectTypePair push(ObjectTypePair obj) {
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$Gson$Preconditions.checkNotNull(obj);
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return stack.push(obj);
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}
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/**
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* Removes the top element from the stack.
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*
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* @return the element being removed from the stack
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* @throws java.util.EmptyStackException thrown if the stack is empty
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*/
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public ObjectTypePair pop() {
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return stack.pop();
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}
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public boolean isEmpty() {
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return stack.isEmpty();
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}
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/**
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* Retrieves the item from the top of the stack, but does not remove it.
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*
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* @return the item from the top of the stack
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* @throws java.util.EmptyStackException thrown if the stack is empty
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*/
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public ObjectTypePair peek() {
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return stack.peek();
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}
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/**
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* Performs a memory reference check to see it the {@code obj} exists in
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* the stack.
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*
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* @param obj the object to search for in the stack
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* @return true if this object is already in the stack otherwise false
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*/
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public boolean contains(ObjectTypePair obj) {
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if (obj == null) {
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return false;
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}
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for (ObjectTypePair stackObject : stack) {
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if (stackObject.getObject() == obj.getObject()
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&& stackObject.type.equals(obj.type) ) {
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return true;
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}
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}
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return false;
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}
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}
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