Java/Regular Expressions/Validation

Find duplication

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; import java.util.regex.PatternSyntaxException; public class MatchDuplicateWords {

 public static void main(String args[]) {
   hasDuplicate("pizza pizza");
   hasDuplicate("Faster pussycat kill kill");
   hasDuplicate("The mayor of of simpleton");
   hasDuplicate("Never Never Never Never Never");
   hasDuplicate("222 2222");
   hasDuplicate("sara sarah");
   hasDuplicate("Faster pussycat kill, kill");
   hasDuplicate(". .");
 }
 public static boolean hasDuplicate(String phrase) {
   boolean retval = false;
   String duplicatePattern = "\\b(\\w+) \\1\\b";
   Pattern p = null;
   try {
     p = Pattern.rupile(duplicatePattern);
   } catch (PatternSyntaxException pex) {
     pex.printStackTrace();
     System.exit(0);
   }
   int matches = 0;
   Matcher m = p.matcher(phrase);
   String val = null;
   while (m.find()) {
     retval = true;
     val = ":" + m.group() + ":";
     System.out.println(val);
     matches++;
   }
   String msg = "   NO MATCH: pattern:" + phrase
       + "\r\n             regex: " + duplicatePattern;
   if (retval) {
     msg = " MATCH     : pattern:" + phrase + "\r\n         regex: "
         + duplicatePattern;
   }
   System.out.println(msg + "\r\n");
   return retval;
 }

}

 </source>
   
  
 
  

Perform credit card validations.

   <source lang="java">

/*

* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import java.io.Serializable; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator;

/**

*

Perform credit card validations.

*

* By default, all supported card types are allowed. You can specify which * cards should pass validation by configuring the validation options. For * example,
CreditCardValidator ccv = new CreditCardValidator(CreditCardValidator.AMEX + CreditCardValidator.VISA); * configures the validator to only pass American Express and Visa cards. * If a card type is not directly supported by this class, you can implement * the CreditCardType interface and pass an instance into the * addAllowedCardType method. *

* For a similar implementation in Perl, reference Sean M. Burke"s
* .
*
* @version $Revision: 478334 $ $Date: 2006-11-22 21:31:54 +0000 (Wed, 22 Nov 2006) $
* @since Validator 1.1
*/

public class CreditCardValidator {

   /**
    * Option specifying that no cards are allowed.  This is useful if
    * you want only custom card types to validate so you turn off the
    * default cards with this option.
    * 

*

     * CreditCardValidator v = new CreditCardValidator(CreditCardValidator.NONE);
     * v.addAllowedCardType(customType);
     * v.isValid(aCardNumber);
     * 

    * @since Validator 1.1.2
    */
   public static final int NONE = 0;
   /**
    * Option specifying that American Express cards are allowed.
    */
   public static final int AMEX = 1 << 0;
   /**
    * Option specifying that Visa cards are allowed.
    */
   public static final int VISA = 1 << 1;
   /**
    * Option specifying that Mastercard cards are allowed.
    */
   public static final int MASTERCARD = 1 << 2;
   /**
    * Option specifying that Discover cards are allowed.
    */
   public static final int DISCOVER = 1 << 3;
   
   /**
    * The CreditCardTypes that are allowed to pass validation.
    */
   private Collection cardTypes = new ArrayList();
   /**
    * Create a new CreditCardValidator with default options.
    */
   public CreditCardValidator() {
       this(AMEX + VISA + MASTERCARD + DISCOVER);
   }
   /**
    * Create a new CreditCardValidator with the specified options.
    * @param options Pass in
    * CreditCardValidator.VISA + CreditCardValidator.AMEX to specify that 
    * those are the only valid card types.
    */
   public CreditCardValidator(int options) {
       super();
       Flags f = new Flags(options);
       if (f.isOn(VISA)) {
           this.cardTypes.add(new Visa());
       }
       if (f.isOn(AMEX)) {
           this.cardTypes.add(new Amex());
       }
       if (f.isOn(MASTERCARD)) {
           this.cardTypes.add(new Mastercard());
       }
       if (f.isOn(DISCOVER)) {
           this.cardTypes.add(new Discover());
       }
   }
   /**
    * Checks if the field is a valid credit card number.
    * @param card The card number to validate.
    * @return Whether the card number is valid.
    */
   public boolean isValid(String card) {
       if ((card == null) || (card.length() < 13) || (card.length() > 19)) {
           return false;
       }
       if (!this.luhnCheck(card)) {
           return false;
       }
       
       Iterator types = this.cardTypes.iterator();
       while (types.hasNext()) {
           CreditCardType type = (CreditCardType) types.next();
           if (type.matches(card)) {
               return true;
           }
       }
       return false;
   }
   
   /**
    * Add an allowed CreditCardType that participates in the card 
    * validation algorithm.
    * @param type The type that is now allowed to pass validation.
    * @since Validator 1.1.2
    */
   public void addAllowedCardType(CreditCardType type){
       this.cardTypes.add(type);
   }
   /**
    * Checks for a valid credit card number.
    * @param cardNumber Credit Card Number.
    * @return Whether the card number passes the luhnCheck.
    */
   protected boolean luhnCheck(String cardNumber) {
       // number must be validated as 0..9 numeric first!!
       int digits = cardNumber.length();
       int oddOrEven = digits & 1;
       long sum = 0;
       for (int count = 0; count < digits; count++) {
           int digit = 0;
           try {
               digit = Integer.parseInt(cardNumber.charAt(count) + "");
           } catch(NumberFormatException e) {
               return false;
           }
           if (((count & 1) ^ oddOrEven) == 0) { // not
               digit *= 2;
               if (digit > 9) {
                   digit -= 9;
               }
           }
           sum += digit;
       }
       return (sum == 0) ? false : (sum % 10 == 0);
   }
   
   /**
    * CreditCardType implementations define how validation is performed
    * for one type/brand of credit card.
    * @since Validator 1.1.2
    */
   public interface CreditCardType {
       
       /**
        * Returns true if the card number matches this type of credit
        * card.  Note that this method is not responsible
        * for analyzing the general form of the card number because 
        * CreditCardValidator performs those checks before 
        * calling this method.  It is generally only required to valid the
        * length and prefix of the number to determine if it"s the correct 
        * type. 
        * @param card The card number, never null.
        * @return true if the number matches.
        */
       boolean matches(String card);
       
   }
   
   /**
    *  Change to support Visa Carte Blue used in France
    *  has been removed - see Bug 35926
    */
   private class Visa implements CreditCardType {
       private static final String PREFIX = "4";
       public boolean matches(String card) {
           return (
               card.substring(0, 1).equals(PREFIX)
                   && (card.length() == 13 || card.length() == 16));
       }
   }
           
   private class Amex implements CreditCardType {
       private static final String PREFIX = "34,37,";
       public boolean matches(String card) {
           String prefix2 = card.substring(0, 2) + ",";
           return ((PREFIX.indexOf(prefix2) != -1) && (card.length() == 15));
       }
   }
   
   private class Discover implements CreditCardType {
       private static final String PREFIX = "6011";
       public boolean matches(String card) {
           return (card.substring(0, 4).equals(PREFIX) && (card.length() == 16));
       }
   }
   
   private class Mastercard implements CreditCardType {
       private static final String PREFIX = "51,52,53,54,55,";
       public boolean matches(String card) {
           String prefix2 = card.substring(0, 2) + ",";
           return ((PREFIX.indexOf(prefix2) != -1) && (card.length() == 16));
       }
   }

}

/**

* Represents a collection of 64 boolean (on/off) flags.  Individual flags 
* are represented by powers of 2.  For example,

* Flag 1 = 1

* Flag 2 = 2

* Flag 3 = 4

* Flag 4 = 8


* or using shift operator to make numbering easier:

* Flag 1 = 1 << 0

* Flag 2 = 1 << 1

* Flag 3 = 1 << 2

* Flag 4 = 1 << 3

* 

*

* There cannot be a flag with a value of 3 because that represents Flag 1 * and Flag 2 both being on/true. *

*
* @version $Revision: 478334 $ $Date: 2006-11-22 21:31:54 +0000 (Wed, 22 Nov 2006) $
*/

class Flags implements Serializable {

   /**
    * Represents the current flag state.
    */
   private long flags = 0;
   /**
    * Create a new Flags object.
    */
   public Flags() {
       super();
   }
   /**
    * Initialize a new Flags object with the given flags.
    *
    * @param flags collection of boolean flags to represent.
    */
   public Flags(long flags) {
       super();
       this.flags = flags;
   }
   /**
    * Returns the current flags.
    *
    * @return collection of boolean flags represented.
    */
   public long getFlags() {
       return this.flags;
   }
   /**
    * Tests whether the given flag is on.  If the flag is not a power of 2 
    * (ie. 3) this tests whether the combination of flags is on.
    *
    * @param flag Flag value to check.
    *
    * @return whether the specified flag value is on.
    */
   public boolean isOn(long flag) {
       return (this.flags & flag) > 0;
   }
   /**
    * Tests whether the given flag is off.  If the flag is not a power of 2 
    * (ie. 3) this tests whether the combination of flags is off.
    *
    * @param flag Flag value to check.
    *
    * @return whether the specified flag value is off.
    */
   public boolean isOff(long flag) {
       return (this.flags & flag) == 0;
   }
   /**
    * Turns on the given flag.  If the flag is not a power of 2 (ie. 3) this
    * turns on multiple flags.
    *
    * @param flag Flag value to turn on.
    */
   public void turnOn(long flag) {
       this.flags |= flag;
   }
   /**
    * Turns off the given flag.  If the flag is not a power of 2 (ie. 3) this
    * turns off multiple flags.
    *
    * @param flag Flag value to turn off.
    */
   public void turnOff(long flag) {
       this.flags &= ~flag;
   }
   /**
    * Turn off all flags.
    */
   public void turnOffAll() {
       this.flags = 0;
   }
   
   /**
    * Turn off all flags.  This is a synonym for turnOffAll().
    * @since Validator 1.1.1
    */
   public void clear() {
       this.flags = 0;
   }
   /**
    * Turn on all 64 flags.
    */
   public void turnOnAll() {
       this.flags = Long.MAX_VALUE;
   }
   /**
    * Clone this Flags object.
    *
    * @return a copy of this object.
    * @see java.lang.Object#clone()
    */
   public Object clone() {
       try {
           return super.clone();
       } catch(CloneNotSupportedException e) {
           throw new RuntimeException("Couldn"t clone Flags object.");
       }
   }
   /**
    * Tests if two Flags objects are in the same state.
    * @param obj object being tested
    * @see java.lang.Object#equals(java.lang.Object)
    *
    * @return whether the objects are equal.
    */
   public boolean equals(Object obj) {
       if (!(obj instanceof Flags)) {
           return false;
       }
       if (obj == this) {
           return true;
       }
       Flags f = (Flags) obj;
       return this.flags == f.flags;
   }
   /**
    * The hash code is based on the current state of the flags.
    * @see java.lang.Object#hashCode()
    *
    * @return the hash code for this object.
    */
   public int hashCode() {
       return (int) this.flags;
   }
   /**
    * Returns a 64 length String with the first flag on the right and the 
    * 64th flag on the left.  A 1 indicates the flag is on, a 0 means it"s 
    * off.
    *
    * @return string representation of this object.
    */
   public String toString() {
       StringBuffer bin = new StringBuffer(Long.toBinaryString(this.flags));
       for (int i = 64 - bin.length(); i > 0; i--) {
           bin.insert(0, "0");
       }
       return bin.toString();
   }

}

 </source>
   
  
 
  

Simplest validation

   <source lang="java">

public class ValidationTest {

 public static void main(String[] args) {
   String candidate = "I love Java and jexp";
   String pattern = "Java \\d";
   System.out.println(candidate.matches(pattern));
 }

}

 </source>
   
  
 
  

Validation with Pattern and Matcher

   <source lang="java">

import java.util.regex.Matcher; import java.util.regex.Pattern; import java.util.regex.PatternSyntaxException; public class ValidationTestWithPatternAndMatcher {

 public static void main(String args[]) {
   Pattern p = null;
   try {
     p = Pattern.rupile("Java \\d");
   } catch (PatternSyntaxException pex) {
     pex.printStackTrace();
     System.exit(0);
   }
   String candidate = "I love Java 5";
   Matcher m = p.matcher(candidate);
   System.out.println("result=" + m.find());
 }

}

 </source>