Java Tutorial/Development/Pattern

Displays directory listing using regular expressions

   <source lang="java">

import java.io.File; import java.io.FilenameFilter; import java.util.Arrays; import java.util.regex.Pattern; public class MainClass {

 public static void main(String[] args) {
   File path = new File(".");
   String[] list;
   if (args.length == 0)
     list = path.list();
   else
     list = path.list(new DirFilter(args[0]));
   Arrays.sort(list);
   for (int i = 0; i < list.length; i++)
     System.out.println(list[i]);
 }

} class DirFilter implements FilenameFilter {

 private Pattern pattern;
 public DirFilter(String regex) {
   pattern = Pattern.rupile(regex);
 }
 public boolean accept(File dir, String name) {
   return pattern.matcher(new File(name).getName()).matches();
 }

}</source>

Pattern.compile("[frb][aiu][gx]).matcher("fix the rug with bags")

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; public class MainClass {

 public static void main(String[] args) throws Exception {
   Matcher m = Pattern.rupile("[frb][aiu][gx]").matcher("fix the rug with bags");
   while (m.find())
     System.out.println(m.group());
   m.reset("fix the rig with rags");
   while (m.find())
     System.out.println(m.group());
 }

} /*

• /</source>

fix
rug
bag
fix
rig
rag

Pattern.compile(^java, Pattern.CASE_INSENSITIVE | Pattern.MULTILINE)

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; public class MainClass {

 public static void main(String[] args) {
   Pattern p = Pattern.rupile("^java", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE);
   Matcher m = p.matcher("java has regex\nJava has regex\n"
       + "JAVA has pretty good regular expressions\n" + "Regular expressions are in Java");
   while (m.find())
     System.out.println(m.group());
 }

} /*

*/</source>
   
  
 
  

java
 Java
 JAVA

Pattern.compile("(?m)(\\S+)\\s+((\\S+)\\s+(\\S+))$").matcher

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; public class MainClass {

 static public final String poem = "PC Bird Cow Slow Doe Hole Joe\n"
     + "Shy Shift Sleep Do Down Doing.\n" + "Yes No How Whose\n";
 public static void main(String[] args) {
   Matcher m = Pattern.rupile("(?m)(\\S+)\\s+((\\S+)\\s+(\\S+))$").matcher(poem);
   while (m.find()) {
     for (int j = 0; j <= m.groupCount(); j++)
       System.out.print("[" + m.group(j) + "]");
     System.out.println();
   }
 }

} /**/</source>

[Doe Hole Joe][Doe][Hole Joe][Hole][Joe]
[Do Down Doing.][Do][Down Doing.][Down][Doing.]
[No How Whose][No][How Whose][How][Whose]

Pattern.compile("!!").split

   <source lang="java">

import java.util.Arrays; import java.util.regex.Pattern; public class MainClass {

 public static void main(String[] args) {
   String input = "This!!unusual use!!of exclamation!!points";
   System.out.println(Arrays.asList(Pattern.rupile("!!").split(input)));

   System.out.println(Arrays.asList(Pattern.rupile("!!").split(input, 3)));
   System.out.println(Arrays.asList("Aha! String has a split() built in!".split(" ")));
 }

} /**/</source>

[This, unusual use, of exclamation, points]
[This, unusual use, of exclamation!!points]
[Aha!, String, has, a, split(), built, in!]

Try out regular expressions

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; public class MainClass {

 public static void main(String[] args) {
   if (args.length < 2) {
     System.out.println("Usage:\n" + "java MainClass " + "characterSequence regularExpression+");
     System.exit(0);
   }
   System.out.println("Input: \"" + args[0] + "\"");
   for (int i = 1; i < args.length; i++) {
     System.out.println("Regular expression: \"" + args[i] + "\"");
     Pattern p = Pattern.rupile(args[i]);
     Matcher m = p.matcher(args[0]);
     while (m.find()) {
       System.out.println("Match \"" + m.group() + "\" at positions " + m.start() + "-"
           + (m.end() - 1));
     }
   }
 }

}</source>