- /*
- * @(#)ArrayQueue.java 1.5 03/12/19
- *
- * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- package com.sun.jmx.remote.internal;
-
- import java.util.AbstractList;
- import java.util.Iterator;
-
- public class ArrayQueue extends AbstractList {
- public ArrayQueue(int capacity) {
- this.capacity = capacity + 1;
- this.queue = new Object[capacity + 1];
- this.head = 0;
- this.tail = 0;
- }
-
- public void resize(int newcapacity) {
- int size = size();
- if (newcapacity < size)
- throw new IndexOutOfBoundsException("Resizing would lose data");
- newcapacity++;
- if (newcapacity == this.capacity)
- return;
- Object[] newqueue = new Object[newcapacity];
- for (int i = 0; i < size; i++)
- newqueue[i] = get(i);
- this.capacity = newcapacity;
- this.queue = newqueue;
- this.head = 0;
- this.tail = size;
- }
-
- public boolean add(Object o) {
- queue[tail] = o;
- int newtail = (tail + 1) % capacity;
- if (newtail == head)
- throw new IndexOutOfBoundsException("Queue full");
- tail = newtail;
- return true; // we did add something
- }
-
- public Object remove(int i) {
- if (i != 0)
- throw new IllegalArgumentException("Can only remove head of queue");
- if (head == tail)
- throw new IndexOutOfBoundsException("Queue empty");
- Object removed = queue[head];
- queue[head] = null;
- head = (head + 1) % capacity;
- return removed;
- }
-
- public Object get(int i) {
- int size = size();
- if (i < 0 || i >= size) {
- final String msg = "Index " + i + ", queue size " + size;
- throw new IndexOutOfBoundsException(msg);
- }
- int index = (head + i) % capacity;
- return queue[index];
- }
-
- public int size() {
- // Can't use % here because it's not mod: -3 % 2 is -1, not +1.
- int diff = tail - head;
- if (diff < 0)
- diff += capacity;
- return diff;
- }
-
- private int capacity;
- private Object[] queue;
- private int head;
- private int tail;
- }