正则表达式

特殊的表达式

零宽断言

Pattern pattern = Pattern.compile("a?");
//零宽断言,所以为true
p("".matches("a*"));			//true
p("weEs".matches("a*"));		//false
p("".matches("a?"));			//true
Matcher matcher = pattern.matcher("fgs");
p(matcher.find());				//true
p("".matches(""));				//true

Matcher的基本用法

Pattern p = Pattern.compile("\\d{3,5}");
String s = "123-34345-234-00";
Matcher m = p.matcher(s);
p(m.matches());					//false
m.reset();						//将匹配位置从maches匹配完的结束位置还原到头部
p(m.find());					//true
p(m.start() + "-" + m.end());	//0-3，start为起始位置，end为结束位置的后一位
p(m.find());					//true
p(m.start() + "-" + m.end());	//4-9
p(m.find());					//true
p(m.start() + "-" + m.end());	//10-13
p(m.find());					//false
//p(m.start() + "-" + m.end());		如果找不到还写start会报异常
p(m.lookingAt());//true	从头部开始找
p(m.lookingAt());//true
p(m.lookingAt());//true
p(m.lookingAt());//true

空白行

p(" \n".matches("^[\\s&&[^\\n]]*\\n$"));
//如果用readLine从文件读取要去掉\\n
p(" \n".matches("^[\\s&&[^\\n]]*$"));

分组（group）

//group,看左小括号，第一个左小括号就是第一组，第二个就是第二组
Pattern pattern = Pattern.compile("(\\d{3,5})([a-z]{2})");
String s = "123aa-34345bb-234cc-00";
Matcher matcher = pattern.matcher(s);
while (matcher.find()) {
    p(matcher.group(1));
    //输出
	/*123
	34345
	2348*/

	p(matcher.group(1));
	//输出
	/*123aa
	34345bb
	234cc*/
}

quantifiers

//Greedy quantifiers 贪婪的量词(从10开始取，如果可以就取10，不可以就往外吐一个接着试探知道成功		输出 0-10
Pattern pattern = Pattern.compile("(.{3,10})[0-9]");
//Reluctant quantifiers 不情愿的量词（从3开始取，如克可以就去3，不可以就吞一个直到可以）		输出 0-5
Pattern pattern = Pattern.compile("(.{3,10}?)[0-9]");
//Possessive quantifiers 占有量词（取10，不往外吐）	输出 not match!
Pattern pattern = Pattern.compile("(.{3,10}+)[0-9]");
String string = "aaaa5bbbb6";
Matcher matcher = pattern.matcher(string);
if (matcher.find()) {
    p(matcher.start() + "-" + matcher.end());
} else {
    p("not match!");
}

Special constructs 特殊构造 (named-capturing and non-capturing命名捕获和非捕获)

(?=a).{3}的意思是从前往后找找开头是a的3个字符，
.{3}(?=a)的意思是从前往后找找结尾后面是a的3个字符
如果你想要包含后面的字符.{3}(?<=a),意思是从后往前找结尾是a的3个字符

//non-capturing groups
//Pattern pattern = Pattern.compile(".{3}(?=a)");	  输出：444
Pattern pattern = Pattern.compile("(?=a).{3}");		//输出：a66
String string = "444a66b";
Matcher matcher = pattern.matcher(string);
while(matcher.find()) {
    p(matcher.group());
}

Back references

(\d(\d))\1后面的\1是重复前面第一个（中的值，第一个\d是1，第二个（\d）是2，所有\1为12
(\d(\d))\2后面的\2是重复前面第二个（中的值，第一个\d是1，第二个（\d）是2，所有\2为2

//back refenrences
Pattern pattern = Pattern.compile("(\\d(\\d))\\1");
String string = "1212";
Matcher matcher = pattern.matcher(string);
p(matcher.matches());

Pattern pattern = Pattern.compile("(\\d(\\d))\\2");
String string = "122";
Matcher matcher = pattern.matcher(string);
p(matcher.matches());

flags的简写

//flags的简写
Pattern pattern = Pattern.compile("java", Pattern.CASE_INSENSITIVE);
p("Java".matches("(?i)(java)"));

抓取网页email邮箱

/*
 * @(#)EmailSpider.java 2019年8月12日上午9:42:45
 * Java
 * Copyright 2019 Thuisoft, Inc. All rights reserved.
 * THUNISOFT PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package regException;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


/**
 * EmailSpider
 * @author Administrator
 * @version 1.0
 *
 */
public class EmailSpider {

    /**
     * @param args
     * 抓取网页中的email地址
     */
    public static void main(String[] args) {
        try {
            BufferedReader bReader = new BufferedReader(new FileReader("E:\\homework\\html\\email.html"));
            String line = "";
            while ((line = bReader.readLine()) != null) {
                parse(line);
            }
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    /**
     * @param line
     */
    private static void parse(String line) {
        Pattern pattern = Pattern.compile("[\\w[.-]]+@[\\w[.-]]+\\.[\\w]+");
        Matcher matcher = pattern.matcher(line);
        while(matcher.find()) {
            System.out.println(matcher.group());
        }
    }

}

统计代码行数

/*
 * @(#)CodeCounter.java 2019年8月12日上午9:55:40
 * Java
 * Copyright 2019 Thuisoft, Inc. All rights reserved.
 * THUNISOFT PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package regException;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

/**
 * CodeCounter
 * @author Administrator
 * @version 1.0
 *
 */
public class CodeCounter {

    static long normalLines = 0;
    static long commentLines = 0;
    static long whiteLines = 0;
    /**
     * @param args
     */
    public static void main(String[] args) {
        File file = new File("E:\\homework\\zhangyi\\src\\com\\thunisoft\\zhangyi\\logic");
        File[] codeFiles = file.listFiles();
        for(File child : codeFiles) {
            if (child.getName().matches(".*\\.java$")) {
                parse(child);
            }
        }
        System.out.println("noramlLines : "+ normalLines);
        System.out.println("commentLines : "+ commentLines);
        System.out.println("whiteLines : "+ whiteLines);
    }
    /**
     * @param file
     */
    private static void parse(File file) {
        BufferedReader bReader = null;
        boolean comment = false;
        try {
            bReader = new BufferedReader(new FileReader(file));
            String line = "";
            while((line = bReader.readLine()) != null) {
                line = line.trim();
                //注意：readLine把每一行最后的\n去掉了
                if (line.matches("^[\\s&&[^\\n]]*$")) {
                    whiteLines++;
                } else if (line.startsWith("/*") || line.startsWith("//")) {
                    commentLines ++;
                    if (line.startsWith("/*") && !line.endsWith("*/")) {
                        comment = true;
                    }
                } else if (true == comment) {
                    commentLines ++;
                    if (line.endsWith("*/")) {
                        comment = false;
                    }
                } else {
                    normalLines ++;
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bReader != null) {
                try {
                    bReader.close();
                    bReader = null;
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        
        
    }

}