读取java文件注释
通过渐进法读取并输出java文件的所有注释/* */和//
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package com.cn.fanjg.regex;
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import java.io.BufferedReader;
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import java.io.FileNotFoundException;
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import java.io.FileReader;
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import java.io.IOException;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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/**
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* @function:打印java文件中的所有注释
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* com.cn.fanjg.regex
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* @author fanjg
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* @date : 2013-4-7 下午06:57:20
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*/
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public class PrintComments {
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public static void main(String[] args) {
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try {
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FileReader freader = new FileReader("./ThreadMain.java");
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BufferedReader breader = new BufferedReader(freader);
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StringBuilder sb = new StringBuilder();
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try {
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String temp = "";
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/**
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* 读取文件内容,并将读取的每一行后都不加\n
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* 其目的是为了在解析双反斜杠(//)注释时做注释中止符
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*/
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while((temp=breader.readLine())!= null)
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{
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sb.append(temp);
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sb.append('\n');
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}
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String src = sb.toString();
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/**
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* 1、做/* 注释的正则匹配
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*
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* 通过渐进法做注释的正则匹配,因为/*注释总是成对出现
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* 当匹配到一个/*时总会在接下来的内容中会首先匹配到"*\\/",
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* 因此在获取对应的"*\\/"注释时只需要从当前匹配的/*开始即可,
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* 下一次匹配时只需要从上一次匹配的结尾开始即可
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* (这样对于大文本可以节省匹配效率)——
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* 这就是渐进匹配法
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*
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* */
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Pattern leftpattern = Pattern.compile("/\\*");
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Matcher leftmatcher = leftpattern.matcher(src);
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Pattern rightpattern = Pattern.compile("\\*/");
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Matcher rightmatcher = rightpattern.matcher(src);
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sb = new StringBuilder();
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/**
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* begin 变量用来做渐进匹配的游标 {@value}
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* 初始值为文件开头
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* **/
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int begin = 0;
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while(leftmatcher.find(begin))
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{
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rightmatcher.find(leftmatcher.start());
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sb.append(src.substring(leftmatcher.start(), rightmatcher.end()));
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/** 为输出时格式的美观 **/
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sb.append('\n');
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begin = rightmatcher.end();
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}
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System.out.println(sb.toString());
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/**
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* 2、对//注释进行匹配(渐进匹配法)
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* 匹配方法是 // 总是与 \n 成对出现
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* */
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begin = 0;
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Pattern leftpattern1 = Pattern.compile("//");
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Matcher leftmatcher1 = leftpattern1.matcher(src);
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Pattern rightpattern1 = Pattern.compile("\n");
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Matcher rightmatcher1 = rightpattern1.matcher(src);
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sb = new StringBuilder();
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while(leftmatcher1.find(begin))
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{
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rightmatcher1.find(leftmatcher1.start());
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sb.append(src.substring(leftmatcher1.start(), rightmatcher1.end()));
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begin = rightmatcher1.end();
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}
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System.out.println(sb.toString());
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} catch (IOException e) {
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System.out.println("文件读取失败");
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}finally
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{
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breader.close();
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freader.close();
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}
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} catch (FileNotFoundException e) {
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System.out.println("文件不存在");
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}catch(IOException e)
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{
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System.out.println("文件读取失败");
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}
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}
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}
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