com.sun.jmx.remote.opt.internal.ArrayQueue Maven / Gradle / Ivy
/*
* @(#)ArrayQueue.java 1.3
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package com.sun.jmx.remote.opt.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;
}