103 lines
3.3 KiB
Java
103 lines
3.3 KiB
Java
/*
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* Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.jmx.remote.internal;
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import java.util.AbstractList;
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import java.util.Iterator;
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public class ArrayQueue<T> extends AbstractList<T> {
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public ArrayQueue(int capacity) {
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this.capacity = capacity + 1;
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this.queue = newArray(capacity + 1);
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this.head = 0;
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this.tail = 0;
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}
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public void resize(int newcapacity) {
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int size = size();
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if (newcapacity < size)
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throw new IndexOutOfBoundsException("Resizing would lose data");
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newcapacity++;
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if (newcapacity == this.capacity)
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return;
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T[] newqueue = newArray(newcapacity);
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for (int i = 0; i < size; i++)
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newqueue[i] = get(i);
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this.capacity = newcapacity;
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this.queue = newqueue;
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this.head = 0;
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this.tail = size;
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}
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@SuppressWarnings("unchecked")
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private T[] newArray(int size) {
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return (T[]) new Object[size];
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}
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public boolean add(T o) {
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queue[tail] = o;
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int newtail = (tail + 1) % capacity;
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if (newtail == head)
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throw new IndexOutOfBoundsException("Queue full");
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tail = newtail;
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return true; // we did add something
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}
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public T remove(int i) {
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if (i != 0)
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throw new IllegalArgumentException("Can only remove head of queue");
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if (head == tail)
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throw new IndexOutOfBoundsException("Queue empty");
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T removed = queue[head];
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queue[head] = null;
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head = (head + 1) % capacity;
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return removed;
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}
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public T get(int i) {
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int size = size();
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if (i < 0 || i >= size) {
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final String msg = "Index " + i + ", queue size " + size;
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throw new IndexOutOfBoundsException(msg);
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}
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int index = (head + i) % capacity;
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return queue[index];
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}
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public int size() {
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// Can't use % here because it's not mod: -3 % 2 is -1, not +1.
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int diff = tail - head;
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if (diff < 0)
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diff += capacity;
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return diff;
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}
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private int capacity;
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private T[] queue;
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private int head;
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private int tail;
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}
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