Java/Regular Expressions/Serialization

Apply Regular Expressions on the contents of a file

   <source lang="java">

import java.io.FileInputStream; import java.nio.ByteBuffer; import java.nio.CharBuffer; import java.nio.channels.FileChannel; import java.nio.charset.Charset; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main {

 public static void main(String[] argv) throws Exception {
   Pattern pattern = Pattern.rupile("pattern");
   FileInputStream input = new FileInputStream("file.txt");
   FileChannel channel = input.getChannel();
   ByteBuffer bbuf = channel.map(FileChannel.MapMode.READ_ONLY, 0, (int) channel.size());
   CharBuffer cbuf = Charset.forName("8859_1").newDecoder().decode(bbuf);
   Matcher matcher = pattern.matcher(cbuf);
   while (matcher.find()) {
     String match = matcher.group();
     System.out.println(match);
   }
 }

}

</source>
   
  
 
  

Reading Lines from a String Using a Regular Expression

   <source lang="java">

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

 public static void main(String[] argv) throws Exception {
   CharSequence inputStr = "a\rb"; 
   inputStr = "a\r\nb"; 
   inputStr = "a\nb"; 
   String patternStr = "^(.*)$";
   Pattern pattern = Pattern.rupile(patternStr, Pattern.MULTILINE);
   Matcher matcher = pattern.matcher(inputStr);
   while (matcher.find()) {
     String lineWithTerminator = matcher.group(0);
     String lineWithoutTerminator = matcher.group(1);
   }
 }

}

</source>
   
  
 
  

Use FileChannels and ByteBuffers to Store Patterns

   <source lang="java">

//Example File /*

1. Email validator that adheres directly to the specification
2. for email address naming. It allows for everything from
3. ipaddress and country-code domains to very rare characters
4. in the username.

email=^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0- 9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0- 9]{1,3})(\]?)$

1. Matches UK postcodes according to the following rules 1. LN NLL
2. eg N1 1AA 2. LLN NLL eg SW4 0QL 3. LNN NLL eg M23 4PJ 4. LLNN NLL
3. eg WS14 0JT 5. LLNL NLL eg SW1N 4TB 6. LNL NLL eg W1C 8LQ Thanks
4. to Simon Bell for informin ...

zip=^[a-zA-Z]{1,2}[0-9][0-9A-Za-z]{0,1} {0,1}[0-9][A-Za-z]{2}$

1. This regular expression matches dates of the form XX/XX/YYYY
2. where XX can be 1 or 2 digits long and YYYY is always 4
3. digits long.

dates=^\d{1,2}\/\d{1,2}\/\d{4}$

• /

import java.util.Properties; import java.util.regex.*; import java.util.*; import java.io.*; import java.nio.*; import java.nio.channels.*; import java.util.logging.Logger; public class RegexProperties extends Properties {

 private static Logger log = Logger.getAnonymousLogger();
 public void load(String inStream) throws IOException,
     PatternSyntaxException {
   load(new FileInputStream(inStream));
 }
 public void load(FileInputStream inStream) throws IOException,
     PatternSyntaxException {
   FileChannel fc = inStream.getChannel();
   ByteBuffer bb = ByteBuffer.allocate((int) fc.size());
   fc.read(bb);
   bb.flip();
   String fileContent = new String(bb.array());
   Pattern pattern = Pattern.rupile("^(.*)$", Pattern.MULTILINE);
   Matcher matcher = pattern.matcher(fileContent);
   while (matcher.find()) {
     String line = matcher.group(1);
     if (line != null && !"".equals(line.trim())
         && !line.startsWith("#") && !line.startsWith("!")) {
       String keyValue[] = null;
       if (line.indexOf("=") > 0)
         keyValue = line.split("=", 2);
       else
         keyValue = line.split(":", 2);
       if (keyValue != null) {
         super.put(keyValue[0].trim(), keyValue[1]);
       }
     }
   }
   fc = null;
   bb = null;
 }
 public void store(FileOutputStream out, String header)
     throws UnsupportedOperationException {
   throw new UnsupportedOperationException("unsupported for this class");
 }
 public void putAll(Map t) {
   throw new UnsupportedOperationException("unsupported for this class");
 }

}

      </source>
   
  
 
  

Using a Regular Expression to Filter Lines from a Reader

   <source lang="java">

import java.io.BufferedReader; import java.io.FileReader; import java.util.regex.Matcher; import java.util.regex.Pattern; public class Main {

 public static void main(String[] argv) throws Exception {
   String filename = "infile.txt";
   String patternStr = "pattern";
   BufferedReader rd = new BufferedReader(new FileReader(filename));
   Pattern pattern = Pattern.rupile(patternStr);
   Matcher matcher = pattern.matcher("\\D");
   String line = null;
   while ((line = rd.readLine()) != null) {
     matcher.reset(line);
     if (matcher.find()) {
       // line matches the pattern
     }
   }
 }

}

</source>