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| 1 | /* | ||
| 2 | * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package com.sun.jmx.remote.internal; | ||
| 27 | |||
| 28 | import java.util.AbstractList; | ||
| 29 | import java.util.Iterator; | ||
| 30 | |||
| 31 | public class ArrayQueue<T> extends AbstractList<T> { | ||
| 32 | public ArrayQueue(int capacity) { | ||
| 33 | this.capacity = capacity + 1; | ||
| 34 | this.queue = newArray(capacity + 1); | ||
| 35 | this.head = 0; | ||
| 36 | this.tail = 0; | ||
| 37 | } | ||
| 38 | |||
| 39 | public void resize(int newcapacity) { | ||
| 40 | int size = size(); | ||
| 41 | if (newcapacity < size) | ||
| 42 | throw new IndexOutOfBoundsException("Resizing would lose data"); | ||
| 43 | newcapacity++; | ||
| 44 | if (newcapacity == this.capacity) | ||
| 45 | return; | ||
| 46 | T[] newqueue = newArray(newcapacity); | ||
| 47 | for (int i = 0; i < size; i++) | ||
| 48 | newqueue[i] = get(i); | ||
| 49 | this.capacity = newcapacity; | ||
| 50 | this.queue = newqueue; | ||
| 51 | this.head = 0; | ||
| 52 | this.tail = size; | ||
| 53 | } | ||
| 54 | |||
| 55 | @SuppressWarnings("unchecked") | ||
| 56 | private T[] newArray(int size) { | ||
| 57 | return (T[]) new Object[size]; | ||
| 58 | } | ||
| 59 | |||
| 60 | public boolean add(T o) { | ||
| 61 | queue[tail] = o; | ||
| 62 | int newtail = (tail + 1) % capacity; | ||
| 63 | if (newtail == head) | ||
| 64 | throw new IndexOutOfBoundsException("Queue full"); | ||
| 65 | tail = newtail; | ||
| 66 | return true; // we did add something | ||
| 67 | } | ||
| 68 | |||
| 69 | public T remove(int i) { | ||
| 70 | if (i != 0) | ||
| 71 | throw new IllegalArgumentException("Can only remove head of queue"); | ||
| 72 | if (head == tail) | ||
| 73 | throw new IndexOutOfBoundsException("Queue empty"); | ||
| 74 | T removed = queue[head]; | ||
| 75 | queue[head] = null; | ||
| 76 | head = (head + 1) % capacity; | ||
| 77 | return removed; | ||
| 78 | } | ||
| 79 | |||
| 80 | public T get(int i) { | ||
| 81 | int size = size(); | ||
| 82 | if (i < 0 || i >= size) { | ||
| 83 | final String msg = "Index " + i + ", queue size " + size; | ||
| 84 | throw new IndexOutOfBoundsException(msg); | ||
| 85 | } | ||
| 86 | int index = (head + i) % capacity; | ||
| 87 | return queue[index]; | ||
| 88 | } | ||
| 89 | |||
| 90 | public int size() { | ||
| 91 | // Can't use % here because it's not mod: -3 % 2 is -1, not +1. | ||
| 92 | int diff = tail - head; | ||
| 93 | if (diff < 0) | ||
| 94 | diff += capacity; | ||
| 95 | return diff; | ||
| 96 | } | ||
| 97 | |||
| 98 | private int capacity; | ||
| 99 | private T[] queue; | ||
| 100 | private int head; | ||
| 101 | private int tail; | ||
| 102 | } | ||