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 26package com.sun.jmx.remote.internal; 27 28import java.util.AbstractList; 29import java.util.Iterator; 30 31public 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} 103