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SPL(Structured Process Language) A programming language specially for structured data computing.

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package com.scudata.common;

import java.util.EmptyStackException;
import java.util.Vector;

/**
 * ???ƴ?С?Ķ?ջ
 */
public final class LimitedStack {

	/**
	 * ??Ա????
	 */
	private int maxSize = Integer.MAX_VALUE;
	/**
	 * ??ջ
	 */
	private Vector stack = new Vector();

	/**
	 * ???캯??
	 */
	public LimitedStack() {
	}

	/**
	 * ???캯??
	 * 
	 * @param maxSize
	 *            ??ջ??󳤶?
	 */
	public LimitedStack(int maxSize) {
		if (maxSize <= 0) {
			throw new IllegalArgumentException("limit must be bigger than 0");
		}
		this.maxSize = maxSize;
	}

	/**
	 * ???ö?ջ??󳤶ȣ?????????????ȵ?ջ??????
	 */
	public void setMaxSize(int maxSize) {
		if (maxSize <= 0) {
			throw new IllegalArgumentException("limit must be bigger than 0");
		}
		this.maxSize = maxSize;
		while (maxSize < size()) {
			stack.removeElementAt(0);
		}
	}

	/**
	 * ȡ??ջ??󳤶?
	 */
	public int getMaxSize() {
		return maxSize;
	}

	/**
	 * ȡ??ջ??Ԫ?ظ???
	 */
	public int size() {
		return stack.size();
	}

	/**
	 * Ԫ?ؽ???ջ??
	 * 
	 * @param item
	 *            ??ջ??Ԫ??
	 */

	public Object push(Object item) {
		if (size() >= maxSize) {
			stack.removeElementAt(0);
		}
		stack.addElement(item);
		return item;
	}

	/**
	 * ջ??Ԫ?س?ջ
	 * 
	 * @return ??ջ??Ԫ??
	 */
	public Object pop() {
		Object obj = peek();
		stack.removeElementAt(size() - 1);
		return obj;
	}

	/**
	 * ȡջ??Ԫ??
	 * 
	 * @return ջ??Ԫ??
	 */
	public Object peek() {
		int len = size();
		if (len == 0) {
			throw new EmptyStackException();
		}
		return stack.elementAt(len - 1);
	}

	/**
	 * ???ջ
	 */
	public void clear() {
		stack.clear();
	}

	/**
	 * ????Ƿ??ջ
	 */
	public boolean empty() {
		return size() == 0;
	}

	/**
	 * ???ջ?Ƿ???
	 */
	public boolean isFull() {
		return size() == maxSize;
	}

	/**
	 * ת?ַ???
	 */
	public String toString() {
		int len = size();
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < len; i++) {
			sb.append(stack.elementAt(i)).append(';');
		}
		return sb.toString();
	}

}
 















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