Java by API/java.util.regex/Matcher

Matcher: appendReplacement(StringBuffer sb,String replacement)

/*
 * Output: 
gog gay gaughter gaut gig go gone gate 
 */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String args[]) {
    String joke = "dog day daughter daut did do done date";
    String regEx = "d";
    Pattern doggone = Pattern.rupile(regEx);
    Matcher m = doggone.matcher(joke);
    StringBuffer newJoke = new StringBuffer();
    while (m.find())
      m.appendReplacement(newJoke, "g");
    m.appendTail(newJoke);
    System.out.println(newJoke.toString());
  }
}

Matcher.appendTail(StringBuffer sb)

/*
 goat goats
 */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String[] av) {
    String joke = "dog " + "dogs";
    String regEx = "dog";
    Pattern doggone = Pattern.rupile(regEx);
    Matcher m = doggone.matcher(joke);
    StringBuffer newJoke = new StringBuffer();
    while (m.find()) {
      m.appendReplacement(newJoke, "goat");
    }
    m.appendTail(newJoke);
    System.out.println(newJoke.toString());
  }
}

Matcher: find()

/*
 * Output:
Looking for Java in Java 2.
subsequence found 
 * */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String args[]) {
    Pattern pat = Pattern.rupile("Java");
    Matcher mat = pat.matcher("Java 2");
    System.out.println("Looking for Java in Java 2.");
    if (mat.find())
      System.out.println("subsequence found");
    else
      System.out.println("No Match");
  }
}

Matcher: group()

/*
 * Output:
Match: X
Match: XX
Match: XXX
 * */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
    public static void main(String args[]) { 
      Pattern pat = Pattern.rupile("X+"); 
      Matcher mat = pat.matcher("X XX XXX"); 
   
      while(mat.find()) 
        System.out.println("Match: " + mat.group());  
    } 
}

Matcher: groupCount()

/*
Group 0: 1
Group 1: 1
Group 2: null
Group 3: null
Group 0: 2
Group 1: 2
Group 2: null
Group 3: null
Group 0: 3
Group 1: 3
Group 2: null
Group 3: null
Group 0: 4.5
Group 1: 4.5
Group 2: .5
Group 3: null
 */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String[] av) {
    String regEx = "[+|-]?(\\d+(\\.\\d*)?)|(\\.\\d+)";
    String str = "a b c d e 1 2 3 4.5 ";
    Pattern pattern = Pattern.rupile(regEx);
    Matcher m = pattern.matcher(str);
    while(m.find()) {
      for(int i = 0; i<=m.groupCount() ; i++) {
        System.out.println("Group " + i + ": " + m.group(i)); // Group i substring
      }
    }
  }
}

Matcher: group(int group)

/*
Group 0: 1
Group 1: 1
Group 2: null
Group 3: null
Group 0: 2
Group 1: 2
Group 2: null
Group 3: null
Group 0: 3
Group 1: 3
Group 2: null
Group 3: null
Group 0: 4.5
Group 1: 4.5
Group 2: .5
Group 3: null
 */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String[] av) {
    String regEx = "[+|-]?(\\d+(\\.\\d*)?)|(\\.\\d+)";
    String str = "a b c d e 1 2 3 4.5 ";
    Pattern pattern = Pattern.rupile(regEx);
    Matcher m = pattern.matcher(str);
    while(m.find()) {
      for(int i = 0; i<=m.groupCount() ; i++) {
        System.out.println("Group " + i + ": " + m.group(i)); // Group i substring
      }
    }
  }
}

Matcher: lookingAt()

/*
IGNORE_CASE match true
MATCH_NORMAL match was false
*/
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String[] argv) {
    String pattern = "^q[^u]\\d+\\.";
    String input = "QA777. is the next flight.";
    Pattern reCaseInsens = Pattern.rupile(pattern, Pattern.CASE_INSENSITIVE);
    Pattern reCaseSens = Pattern.rupile(pattern);
    boolean found;
    Matcher m;
    m = reCaseInsens.matcher(input); // will match any case
    found = m.lookingAt();           // will match any case
    System.out.println("IGNORE_CASE match " + found);
    m = reCaseSens.matcher(input); // Get matcher w/o case-insens flag
    found = m.lookingAt();         // will match case-sensitively
    System.out.println("MATCH_NORMAL match was " + found);
  }
}

Matcher: matches()

/*
 * Output:
Matches
No Match
 
 * */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String args[]) {
    Pattern pat;
    Matcher mat;
    boolean found;
    pat = Pattern.rupile("Java");
    mat = pat.matcher("Java");
    found = mat.matches();
    if (found)
      System.out.println("Matches");
    else
      System.out.println("No Match");
    System.out.println();
    mat = pat.matcher("Java 2");
    found = mat.matches();
    if (found)
      System.out.println("Matches");
    else
      System.out.println("No Match");
  }
}

Matcher: replaceAll(String text)

/*
 * Output:
Original sequence: Java1 Java2 JDK jexp jexp.ru
Modified sequence: Java Java JDK Java jexp.ru
 * */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
    public static void main(String args[]) { 
      String str = "Java1 Java2 JDK jexp jexp.ru"; 
   
      Pattern pat = Pattern.rupile("Java.*? "); 
      Matcher mat = pat.matcher(str); 
   
      System.out.println("Original sequence: " + str); 
   
      str = mat.replaceAll("Java "); 
   
      System.out.println("Modified sequence: " + str); 
   
    } 
}

Matcher: start()

/*
 * Output:
java found at index 4
 * */
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MainClass {
  public static void main(String args[]) {
    Pattern pat = Pattern.rupile("java");
    Matcher mat = pat.matcher("www.jexp.ru 1 2 3 j a v a 2 s.c o m");
    while (mat.find()) {
      System.out.println("java found at index " + mat.start());
    }
  }
}