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// Regex pattern describe any character.
String regex = "."; 
// Regex pattern describe a dot character.
String regex = "\\.";

...
 
// Check the entire String object matches the regex or not.
public boolean matches(String regex)
..

package org.wikitechy.tutorial.regex.stringmatches;
 
public class StringMatches {
 
    public static void main(String[] args) {
 
        String s1 = "a";
        System.out.println("s1=" + s1);
 
        // Check the entire s1
        // Match any character
        // Rule .
        // ==> true
        boolean match = s1.matches(".");
        System.out.println("-Match . " + match);
 
        s1 = "abc";
        System.out.println("s1=" + s1);
 
        // Check the entire s1
        // Match any character
        // Rule .
        // ==> false (Because s1 has three characters)
        match = s1.matches(".");
        System.out.println("-Match . " + match);
 
        // Check the entire s1
        // Match with any character 0 or more times
        // Combine the rules . and *
        // ==> true
        match = s1.matches(".*");
        System.out.println("-Match .* " + match);
 
        String s2 = "m";
        System.out.println("s2=" + s2);
 
        // Check the entire s2
        // Start by m
        // Rule ^
        // ==> true
        match = s2.matches("^m");
        System.out.println("-Match ^m " + match);
 
        s2 = "mnp";
        System.out.println("s2=" + s2);
 
        // Check the entire s2
        // Start by m
        // Rule ^
        // ==> false (Because s2 has three characters)
        match = s2.matches("^m");
        System.out.println("-Match ^m " + match);
 
        // Start by m
        // Next any character, appearing one or more times.
        // Rule ^ and. and +
        // ==> true
        match = s2.matches("^m.+");
        System.out.println("-Match ^m.+ " + match);
 
        String s3 = "p";
        System.out.println("s3=" + s3);
 
        // Check s3 ending with p
        // Rule $
        // ==> true
        match = s3.matches("p$");
        System.out.println("-Match p$ " + match);
 
        s3 = "2nnp";
        System.out.println("s3=" + s3);
 
        // Check the entire s3
        // End of p
        // ==> false (Because s3 has 4 characters)
        match = s3.matches("p$");
        System.out.println("-Match p$ " + match);
 
        // Check out the entire s3
        // Any character appearing once.
        // Followed by n, appear one or up to three times.
        // End by p: p $
        // Combine the rules: . , {X, y}, $
        // ==> true
 
        match = s3.matches(".n{1,3}p$");
        System.out.println("-Match .n{1,3}p$ " + match);
 
        String s4 = "2ybcd";
        System.out.println("s4=" + s4);
 
        // Start by 2
        // Next x or y or z
        // Followed by any one or more times.
        // Combine the rules: [abc]. , +
        // ==> true
        match = s4.matches("2[xyz].+");
 
        System.out.println("-Match 2[xyz].+ " + match);
 
        String s5 = "2bkbv";
         
        // Start any one or more times
        // Followed by a or b, or c: [abc]
        // Next z or v: [zv]
        // Followed by any
        // ==> true
        match = s5.matches(".+[abc][zv].*");
 
        System.out.println("-Match .+[abc][zv].* " + match);
    }
 
}

package org.wikitechy.tutorial.regex.stringmatches;
 
public class SplitWithRegex {
 
    public static final String TEXT = "This is my text";
 
    public static void main(String[] args) {
        System.out.println("TEXT=" + TEXT);
          
        // White space appears one or more times.
        // The whitespace characters: \t \n \x0b \r \f
        // Combining rules: \ s and +        
        String regex = "\\s+";
        String[] splitString = TEXT.split(regex);
        // 4
        System.out.println(splitString.length);
 
        for (String string : splitString) {
            System.out.println(string);
        }
        // Replace all whitespace with tabs
        String newText = TEXT.replaceAll("\\s+", "\t");
        System.out.println("New text=" + newText);
    }
}

package org.wikitechy.tutorial.regex.stringmatches;
 
public class EitherOrCheck {
 
    public static void main(String[] args) {
 
        String s = "The film Tom and Jerry!";
  
        // Check the whole s
        // Begin by any characters appear 0 or more times
        // Next Tom or Jerry
        // End with any characters appear 0 or more times
        // Combine the rules:., *, X | Z
        // ==> true        
        boolean match = s.matches(".*(Tom|Jerry).*");
        System.out.println("s=" + s);
        System.out.println("-Match .*(Tom|Jerry).* " + match);
 
        s = "The cat";
        // ==> false
        match = s.matches(".*(Tom|Jerry).*");
        System.out.println("s=" + s);
        System.out.println("-Match .*(Tom|Jerry).* " + match);
 
        s = "The Tom cat";
        // ==> true
        match = s.matches(".*(Tom|Jerry).*");
        System.out.println("s=" + s);
        System.out.println("-Match .*(Tom|Jerry).* " + match);
    }
 
}

String regex= ".xx.";
// Create a Pattern object through a static method.
Pattern pattern = Pattern.compile(regex);
// Get a Matcher object
Matcher matcher = pattern.matcher("MxxY");
 
boolean match = matcher.matches();
 
System.out.println("Match "+ match);

public static Pattern compile(String regex, int flags) ;
 
public static Pattern compile(String regex);
 
public Matcher matcher(CharSequence input);
 
public static boolean matches(String regex, CharSequence input);

public int start()
 
public int start(int group)
 
public int end()
 
public int end(int group)
 
public String group()
 
public String group(int group)
 
public String group(String name)
 
public int groupCount()
 
public boolean matches()
 
public boolean lookingAt()
 
public boolean find()

package org.wikitechy.tutorial.regex;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class MatcherFind {
 
   public static void main(String[] args) {
 
       final String TEXT = "This \t is a \t\t\t String";
 
       // Spaces appears one or more time.
       String regex = "\\s+";
 
       Pattern pattern = Pattern.compile(regex);
 
       Matcher matcher = pattern.matcher(TEXT);
 
       int i = 0;
       while (matcher.find()) {
           System.out.print("start" + i + " = " + matcher.start());
           System.out.print(" end" + i + " = " + matcher.end());
           System.out.println(" group" + i + " = " + matcher.group());
           i++;
       }
 
   }
}

package org.wikitechy.tutorial.regex;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class MatcherLookingAt {
 
    public static void main(String[] args) {
        String country1 = "iran";
        String country2 = "Iraq";
 
        // Start by I followed by any character.
        // Following is the letter a or e.
        String regex = "^I.[ae]";
 
        Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
 
        Matcher matcher = pattern.matcher(country1);
 
        // lookingAt () searches that match the first part.
        System.out.println("lookingAt = " + matcher.lookingAt());
 
        // matches() must be matching the entire
        System.out.println("matches = " + matcher.matches());
 
        // Reset matcher with new text: country2
        matcher.reset(country2);
 
        System.out.println("lookingAt = " + matcher.lookingAt());
        System.out.println("matches = " + matcher.matches());
    }
}

// A regular expression
String regex = "\\s+=\\d+";
 
// Writing as three group, by marking ()
String regex2 = "(\\s+)(=)(\\d+)";
 
// Two group
String regex3 = "(\\s+)(=\\d+)";

package org.wikitechy.tutorial.regex;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class NamedGroup {
 
   public static void main(String[] args) {
 
    
       final String TEXT = " int a = 100;float b= 130;float c= 110 ; ";
 
        // Use (?<groupName>pattern) to define a group named: groupName
        // Defined group named declare: using (?<declare>...)
        // And a group named value: use: (?<value>..)
       String regex = "(?<declare>\\s*(int|float)\\s+[a-z]\\s*)=(?<value>\\s*\\d+\\s*);";
 
       Pattern pattern = Pattern.compile(regex);
 
       Matcher matcher = pattern.matcher(TEXT);
 
       while (matcher.find()) {
           String group = matcher.group();
           System.out.println(group);
           System.out.println("declare: " + matcher.group("declare"));
           System.out.println("value: " + matcher.group("value"));
           System.out.println("------------------------------");
       }
   }
}

// This is a regex
// any characters appear 0 or more times,
// followed by ' and >
String regex = ".*'>";
 
// TEXT1 match the regex.
String TEXT1 = "FILE1'>";
 
// And TEXT2 match the regex
String TEXT2 = "FILE1'> <a href='http://HOST/file/FILE2'>";

package org.wikitechy.tutorial.regex;
 
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class NamedGroup2 {
 
  public static void main(String[] args) {
      String TEXT = "<a href='http://HOST/file/FILE1'>File 1</a>"
              + "<a href='http://HOST/file/FILE2'>File 2</a>";
 
      // Java >= 7.
      // Define group named fileName.
      // *? ==> ? after a quantifier makes it a reluctant quantifier.
      // It tries to find the smallest match.
      String regex = "/file/(?<fileName>.*?)'>";
 
      Pattern pattern = Pattern.compile(regex);
      Matcher matcher = pattern.matcher(TEXT);
 
      while (matcher.find()) {
          System.out.println("File Name = " + matcher.group("fileName"));
      }
  }
 
}