正则表达式

正则表达式：

         正则表达式对字符串的常见操作

           1.匹配

                            其实使用的就是String类中的matches方法

                            Stringtel = "1232131212";

                            Stringregex = "1[358][0-9]{9}"//"1[358]\\d{9}"

                            booleanb = tel.matches(regex);

           2.切割

                            其实使用的就是String类中的split()方法

                            Stringstr = "ads   sd s   sd";

                            String[]name = str.split(" +");用一个或者多个空格进行切割

                           

                            "\\."第一个\转义第二个\第二个\转义.

                            "(.)\\1+"   zhangtttkkad

                            使用()来表示组，表示第一组是任意字符，然后第二位和第一组相同

                            并且第二位使用转义字符，然后最少一次

           3.替换

                            其实使用的就是String类中的replaceAll()方法

                            Stringstr = "adsdfsddddasadfd";

                            str= str.replaceAll("(.)\\1+","$1");

                            使用$符号来表示第二个参数使用的是第一个正则表达式中的第一组

                           

                            Stringstr = "1230000123";

                            str= str.replaceAll("(\\d{3})\\d{4}(\\d{3})","$1****$2");

                            第一组和第二组保持一致，中间替换

           4.获取

                            将正则规则进行对象的封装

                            Patternp = Pattern.compile("a*b");

                            通过正则对象的matcher方法和字符串关联，获取要对字符串操作的匹配对象Matcher

                            Matcherm = p.matcher("aaaab");

                            通过Matcher匹配器对象的方法对字符串进行操作

                            booleanb = m.matches();

                            获取三个字母的单词

                            Stringstr = "duan wujie bu fang jia!";

                            Stringregex = "\\b[a-z]{3}\\b"  \\b是字符边界

                            将正则封装成对象

                            Patternp = Pattern.compile(regex);

                            通过正则对象获取匹配对象

                            Matcherm = p.matcher(str);

                            while(m.find()){

                                     syso(m.group())//拿到单词

                                     syso(m.start()+""+m.end());//该单词字母所在字符串的位置

                            }

           应用：

治疗口吃：

1.      我我.我...我要要要...要要学学学..学习习...习习习编编编.....编编编程程程....程程

                                     publicstatic void test_1(){

                                               Stringstr = "我我.我...我要要要...要要学学学..学习";

                                               1.去掉字符串中.。

                                               str= str.replaceAll("\\.+","");

                                               2.替换叠词

                                               str= str.replaceAll("(.)\\1+","$1");

                                               syso(str);

                                     }

                     2.对ip地址排序

                                     Stringstr_ip = "192.168.1.1 1.1.1.1 33.4.5.6";

                                     str_ip= str_ip.replaceAll("(\\d+)","00$1");

                                     str_ip= str_ip.replaceAll("0*(\\d{3})","$1");

                                     String[]ips = str_ip.split(" +");

                                     TreeSet<String>ts = new TreeSet<String>();

                                     for(Stingip:ips){

                                               ts.add(ip);

                                     }

                                     for(Stingip:ts){

                                               syso(ip.replaceAll("0*(\\d+)","$1"));

                                     }

                     3.对邮件地址校验

                                     Stringregex = "\\w+@\\w+(\\.\\w+)+";

              网页爬虫

                                               privatestatic List<String> getMailsByWeb() throws IOException {

                                     //定义统一资源定位符对象

                                     URLurl = new URL("http://lib.sdut.edu.cn/index.html");

                                     BufferedReaderbufr = new BufferedReader(new InputStreamReader(url.openStream()));

                                     //定义一个规则

                                     Stringregex = "\\w+@\\w+(\\.\\w+)+";

                                     //获取符合规则的字符

                                     //创建模式规则对象

                                     Patternp  = Pattern.compile(regex);

                                     Stringline = null;

                                     List<String>list = new ArrayList<String>();

                                     while((line= bufr.readLine())!=null){

                                               //创建匹配对象

                                               Matchermatcher = p.matcher(line);

                                               while(matcher.find()){

                                                        list.add(matcher.group());

                                               }

                                     }

                                     returnlist;

                            }