Question

我创建了一个简单的评论检测代码。

import javax.swing.*;
import java.util.regex.*;
import java.awt.*;
import java.awt.event.*;
public class regex extends JFrame implements ActionListener
{
    JPanel center=new JPanel();
    JPanel title=new JPanel();
    JTextArea text=new JTextArea();
    JTextArea result=new JTextArea();
    JScrollPane sctext=new JScrollPane(text);
    JScrollPane scresult=new JScrollPane(result);
    JButton proc=new JButton("proccess");
    regex()
    {
        setSize(600,600);
        setLayout(new BorderLayout());
        add(title,BorderLayout.NORTH);
        title.setLayout(new GridLayout(1,2));
        title.add(new JLabel("code"));
        title.add(new JLabel("Regex"));
        add(center,BorderLayout.CENTER);
        center.setLayout(new GridLayout(1,2));
        center.add(sctext);
        center.add(scresult);
        add(proc,BorderLayout.SOUTH);
        proc.addActionListener(this);
        show();
    }
    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource()==proc)
        {
            try
            {
                result.setText("");
                Matcher m=Pattern.compile("(/\\*(.|[\\n]|(\\*+([^*/]|[\\r\\n])))*\\*+/)|(//.*)").matcher(text.getText());
                while(m.find())
                {
                    result.append(m.group()+"\n");
                }
            }
            catch(Exception x)
            {
                try
                {
                    File err = new File("error.txt");
                    java.io.PrintStream ps = new java.io.PrintStream(err);
                    x.printStackTrace(ps);
                    ps.close();
                }
                catch(Exception exx){}
            }
        }
    }
    public static void main(String[]agrs)
    {
        new regex();
    }
}

我不知道为什么我的代码无法检测到长评论。
我有一个包含长评论的文本样本。

/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:  
 *       "This product includes software developed by the 
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

但它正致力于发表短评。

程序捕获大量错误

code error

Answer 1

Java正则表达式引擎似乎是基于递归的。这意味着必须优化正则表达式以产生更少的回溯。然而，我无法看到哪个回溯产生了这个调用堆栈。

以下提案适用于更大的评论：

Pattern.compile("(/\\*.*?\\*/)", Pattern.DOTALL)（仅匹配/ * .. * /）
Pattern.compile("(/\\*([^\\*]|(\\*(?!/))+)*+\\*+/)|(//.*)")

说明：

(.| ...)*通常会产生回溯，因为.匹配（几乎）所有字符，其他选项通常也匹配.* - 因此第一个操作是消除.。在您的情况下，请将其替换为[^\\*]。
[^\\*]|[\\n] == [^\\*]请删除[\\n]
[^*/]|[\\r\\n] == [^*/]请删除[\\r\\n]
为防止回溯，我们在内容循环（占有式正则表达式）后使用*+。但这要求内容循环不消耗最后一个点。因此，我们会在匹配的/之后为*插入否定的循环，即(\\*(?!/))+

使用java中的正则表达式进行注释检测时出错

1 个答案: