用java代码写一个堆栈

    public class WorkerStack {
        
        protected Worker[] workers = null;
        protected int end = 0;
        
        public WorkerStack(int size) {
            workers = new Worker[size];
        }
        
        /** 
         * Put the object into the queue. If the queue is full (for example if
         * the queue has been reduced in size) the object will be dropped.
         * 
         * @param   object  the object to be appended to the queue (first
         *                  element).
         */
        public void push(Worker worker) {
            if (end < workers.length) {
                workers[end++] = worker;
            } else {
                curThreads--;
            }
        }
        
        /**
         * Get the first object out of the queue. Return null if the queue
         * is empty. 
         */
        public Worker pop() {
            if (end > 0) {
                return workers[--end];
            }
            return null;
        }
        
        /**
         * Get the first object out of the queue, Return null if the queue
         * is empty.
         */
        public Worker peek() {
            return workers[end];
        }
        
        /**
         * Is the queue empty?
         */
        public boolean isEmpty() {
            return (end == 0);
        }
        
        /**
         * How many elements are there in this queue?
         */
        public int size() {
            return (end);
        }
        
        /**
         * Resize the queue. If there are too many objects in the queue for the
         * new size, drop the excess.
         * 
         * @param newSize
         */
        public void resize(int newSize) {
            Worker[] newWorkers = new Worker[newSize];
            int len = workers.length;
            if (newSize < len) {
                len = newSize;
            }
            System.arraycopy(workers, 0, newWorkers, 0, len);
            workers = newWorkers;
        }
    }

 以上代码来源于Tomcat 6源码