Java Support for regular Expressions (ii)

The primary use of regular expressions:

A. Finding the part of a matching regular expression in the target string

B. Verifying that the target string conforms to a regular expression, such as verifying an email address

C. Replacing a part of a regular expression with another string in the target string

The scanner class is the scan class introduced in JDK 1.5, and the constructor of the scanner class can accept a readable object, specifically file, String, InputStream, and so on.

The following is an example of a scanner class with regular expressions to find words that begin with S, S, C, T.

 Packageregextest;ImportJava.io.File;Importjava.io.FileNotFoundException;ImportJava.util.Scanner;ImportJava.util.regex.Matcher;ImportJava.util.regex.Pattern; Public classScannertest { Public Static voidMain (String [] args)throwsfilenotfoundexception {Pattern pa= Pattern.compile ("\\b[ssct]\\w+"); Matcher Ma= Pa.matcher (""); Scanner SC=NewScanner (NewFile ("Src/regextest/scannertest.java"));  while(Sc.hasnextline ()) {Ma.reset (Sc.nextline ());  while(Ma.find ()) {System.out.println (Ma.group ()); }        }    }    }

The output is:

Scanner class scannertest Static String throws Compilessctscannerscscannersrcscannertestscscsystem

The meaning of the regular expression "\\b[ssct]\\w+" is as follows, \b represents the boundary of a word, and \b is used to manipulate words using regular expressions. W stands for 0-9 or a-Z or a-Z.

Sc.hasnextline () can determine if scanner can take the next line, Sc.nextline () is a string that takes a line off.

Scanner also has Hasnextint (), Hasnextlong (), Hasnextbiginteger () and other methods for removing the next basic type.

The scanner default is to divide the input string by space, or you can customize the delimiter, as shown below.

Import Java.util.Scanner;  Public class ScannerTest2 {    publicstaticvoid  main (String [] args) {        = " 12,42, the  ",";                 New Scanner (str);        Sc.usedelimiter ("\\s*,\\s*");          while (Sc.hasnextint ()) {            System.out.println (Sc.nextint ());     }}}

The output is:

1242789942

Sc.usedelimiter ("\\s*,\\s*"), in which the \s represents a blank character (space, carriage return, line feed, etc.), * represents one or more, together is "," with any whitespace character before and after.

Scanner, in addition to being able to work with pattern and matcher, also supports regular expressions, as in the following example.

 Packageregextest;ImportJava.util.Scanner;ImportJava.util.regex.MatchResult;ImportJava.util.regex.Matcher;ImportJava.util.regex.Pattern; Public classScannerTest3 { Public Static voidmain (string [] args) {string str= "[Email protected]/10/2012\n" + "[email protected]/11/2012\n" + "[email protecte d]/12/2012\n "+" [email protected]/12/2012\n]; Scanner SC=NewScanner (str); String pattern= "(\\d+\\.\\d+\\.\\d+\\.\\d+) @" + "(\\d{2}/\\d{2}/\\d{4})";  while(Sc.hasnext (pattern)) {Sc.next (pattern); Matchresult Mr=Sc.match (); String IP= Mr.group (1); String Date= Mr.group (2); System.out.format ("Threat on%s from%s\n", DATE,IP); } Pattern PA= Pattern.compile ("(\\d+\\.\\d+\\.\\d+\\.\\d+) @" + "(\\d{2}/\\d{2}/\\d{4})", Pattern.case_insensitive |pattern.multiline); Matcher Matcher=Pa.matcher (str);  while(Matcher.find ()) {String IP= Matcher.group (1); String Date= Matcher.group (2); System.out.format ("Threat on%s from%s\n", DATE,IP); }    }    }

The output is:

Threat on 02/10/2012 from 58.77.82.16102/11/2012 to 204.17.82.3102/12/2012 from 58.77.32.53 02/12/2012 from 28.45.32.16102/10/2012 to 58.77.82.16102/11/2012 from 204.17.82.31  02/12/2012 from 58.77.32.5302/12/2012 from 28.45.32.161

Java Support for regular Expressions (ii)