Regular expression one of Java se: overview

The concept of regular expressions

• Definition: An expression that conforms to a certain rule
• Function: Used to specialize in manipulating strings

• Features: For some specific symbols to represent the operation of the Code, thus simplifying the lengthy program code

• Benefit: simplifies complex manipulation of strings

• Cons: The more symbols are defined, the longer the regular, the worse the reading

Key classes

• String
• Pattern: Regular Class object
• Matcher: The engine class that performs a matching operation on the character sequence by interpreting the pattern. (Matching device)

Specific operation function Matching: Returns Boolean value that matches the rule

1 String:    boolean string.matches(String regex)2 Pattern + Matcher:    Pattern pattern.compile(String regex)    Matcher pattern.matcher(String regex)     boolean matcher.matches()3 Pattern    boolean b = Pattern.matches(String regex, String string)

Cut: Returns a string other than the match rule

1 String:String[] split(String regex)2 String:String[] split(String regex, int limit)> 为了让规则的结果被重用，可以让规则封装成一个组，用()完成。组的出现都有编号：    从1开始想要使用已有的组可以通过格式：\ + 组序号    Eg:以叠词作为分隔符号，切隔字符串:(.)\1+    Eg:     (X(Y(Z)))(M)        组号：1 2 3    4   

Replace: Returns the string replaced by the rule

1 String:String replaceAll(String regex, String replacement):regex-\n2 String:String replaceFirst(String regex, String replacement):replacement-$n3 Pattern + Matcher:    Pattern pattern.compile(String regex)    Matcher pattern.matcher(String regex)     -------------------------------------    String matcher.quoteReplacement(String s)    String matcher.replaceAll(String replacement)    

Get: Remove a substring of a rule in a string

将正则表达式封装成对象；让正则表达式和要操作的字符串相关联；关联后，获取正则匹配引擎；通过引擎对符合规则的子串进行操作，如：取出1   //step1:将规则封装成对象    Pattern pattern = Pattern.compile(regex);        //step2：让正则对象和要提取的字符串相关联,获取匹配(器)引擎对象    Matcher matcher = pattern.matcher(string);        while(matcher.find()) {//不断地利用正则引擎查找符合正则表达式的对象,找到：true；没有找到：false        System.out.println("start:" + matcher.start() + " word:" + matcher.group() + " end:" + matcher.end());//返回当前查找到的一个子串，并返回其单词的开始start()与结束区间end()    }

Reference documents

[黑马程序员_毕向东_Java基础视频教程第25天](http://www.huahuionline.com/MainCtrl?page=ShowLessonDetailPage&lesson_id=56c1838945ceb61ab5246f3d&cNo=1)

Regular expression one of Java se: overview