Java/Regular Expressions/Lookup

Java Regular Expression : File and Find

/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public final class RegexTestHarness {
  private static String REGEX;
  private static String INPUT;
  private static BufferedReader br;
  private static Pattern pattern;
  private static Matcher matcher;
  private static boolean found;
  public static void main(String[] argv) {
    initResources();
    processTest();
    closeResources();
  }
  private static void initResources() {
    try {
      br = new BufferedReader(new FileReader("regex.txt"));
    } catch (FileNotFoundException fnfe) {
      System.out
          .println("Cannot locate input file! " + fnfe.getMessage());
      System.exit(0);
    }
    try {
      REGEX = br.readLine();
      INPUT = br.readLine();
    } catch (IOException ioe) {
    }
    pattern = Pattern.rupile(REGEX);
    matcher = pattern.matcher(INPUT);
    System.out.println("Current REGEX is: " + REGEX);
    System.out.println("Current INPUT is: " + INPUT);
  }
  private static void processTest() {
    while (matcher.find()) {
      System.out.println("I found the text \"" + matcher.group()
          + "\" starting at index " + matcher.start()
          + " and ending at index " + matcher.end() + ".");
      found = true;
    }
    if (!found) {
      System.out.println("No match found.");
    }
  }
  private static void closeResources() {
    try {
      br.close();
    } catch (IOException ioe) {
    }
  }
}

Java Regular Expression : find 2

/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
public final class RegexTestHarness2 {
  private static String REGEX;
  private static String INPUT;
  private static BufferedReader br;
  private static Pattern pattern;
  private static Matcher matcher;
  private static boolean found;
  public static void main(String[] argv) {
    initResources();
    processTest();
    closeResources();
  }
  private static void initResources() {
    try {
      br = new BufferedReader(new FileReader("regex.txt"));
    } catch (FileNotFoundException fnfe) {
      System.out
          .println("Cannot locate input file! " + fnfe.getMessage());
      System.exit(0);
    }
    try {
      REGEX = br.readLine();
      INPUT = br.readLine();
    } catch (IOException ioe) {
    }
    try {
      pattern = Pattern.rupile(REGEX);
      matcher = pattern.matcher(INPUT);
    } catch (PatternSyntaxException pse) {
      System.out
          .println("There is a problem with the regular expression!");
      System.out.println("The pattern in question is: "
          + pse.getPattern());
      System.out.println("The description is: " + pse.getDescription());
      System.out.println("The message is: " + pse.getMessage());
      System.out.println("The index is: " + pse.getIndex());
      System.exit(0);
    }
    System.out.println("Current REGEX is: " + REGEX);
    System.out.println("Current INPUT is: " + INPUT);
  }
  private static void processTest() {
    while (matcher.find()) {
      System.out.println("I found the text \"" + matcher.group()
          + "\" starting at index " + matcher.start()
          + " and ending at index " + matcher.end() + ".");
      found = true;
    }
    if (!found) {
      System.out.println("No match found.");
    }
  }
  private static void closeResources() {
    try {
      br.close();
    } catch (IOException ioe) {
    }
  }
}

Negative Look ahead

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class NegativeLookaheadExample {
  public static void main(String args[]) throws Exception {
    String regex = "John (?!Smith)[A-Z]\\w+";
    Pattern pattern = Pattern.rupile(regex);
    String candidate = "I think that John Smith ";
    candidate += "is a fictional character. His real name ";
    candidate += "might be John Jackson, John Westling, ";
    candidate += "or John Holmes for all we know.";
    Matcher matcher = pattern.matcher(candidate);
    String tmp = null;
    while (matcher.find()) {
      tmp = matcher.group();
      System.out.println("MATCH:" + tmp);
    }
  }
}

Positive Look ahead

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PositiveLookaheadExample {
  public static void main(String args[]) {
    String regex = "(?=^255).*";
    Pattern pattern = Pattern.rupile(regex);
    String candidate = "255.0.0.1";
    Matcher matcher = pattern.matcher(candidate);
    String ip = "not found";
    if (matcher.find())
      ip = matcher.group();
    String msg = "ip: " + ip;
    System.out.println(msg);
  }
}

Positive Look behind 1

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PositiveLookBehindExample {
  public static void main(String args[]) throws Exception {
    String regex = "(?<=http://)\\S+";
    Pattern pattern = Pattern.rupile(regex);
    String candidate = "The jexp website can be found at ";
    candidate += "http://www.jexp.ru. There, ";
    candidate += "you can find some Java examples.";
    Matcher matcher = pattern.matcher(candidate);
    while (matcher.find()) {
      String msg = ":" + matcher.group() + ":";
      System.out.println(msg);
    }
  }
}

Positive Look Behind 2

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PositiveLookBehindExample {
  public static void main(String args[]) throws Exception {
    String regex = "(?<=http://)\\S+";
    Pattern pattern = Pattern.rupile(regex);
    String candidate = "The jexp website can be found at ";
    candidate += "http://www.jexp.ru. There, ";
    candidate += "you can find some best example code for Java.";
    Matcher matcher = pattern.matcher(candidate);
    while (matcher.find()) {
      String msg = ":" + matcher.group() + ":";
      System.out.println(msg);
    }
  }
}

Positive Look Behind 3

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class PositiveLookBehindExample {
  public static void main(String args[]) throws Exception {
    String regex = "(?<=http://)\\S+";
    Pattern pattern = Pattern.rupile(regex);
    String candidate = "The jexp website can be found at ";
    candidate += "http://www.jexp.ru. There, ";
    candidate += "you can find information about some of ";
    candidate += "best example codes";
    Matcher matcher = pattern.matcher(candidate);
    while (matcher.find()) {
      String msg = ":" + matcher.group() + ":";
      System.out.println(msg);
    }
  }
}

Regular Expression: find

/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public final class MatcherTest {
  private static final String REGEX = "\\bdog\\b";
  private static final String INPUT = "dog dog dog doggie dogg";
  public static void main(String[] argv) {
    Pattern p = Pattern.rupile(REGEX);
    Matcher m = p.matcher(INPUT); // get a matcher object
    int count = 0;
    while (m.find()) {
      count++;
      System.out.println("Match number " + count);
      System.out.println("start(): " + m.start());
      System.out.println("end(): " + m.end());
    }
  }
}