CharMatcher Class in Java

The CharMatcher class determines a true or false value for any Java char value, just as Predicate does for any Object.

Sr.No	Methods & Description
1	CharMatcher and(CharMatcher other)Returns a matcher that matches any character matched by both this matcher and other.
2	static CharMatcher anyOf(CharSequence sequence)Returns a char matcher that matches any character present in the given character sequence.
3	boolean apply(Character character)Deprecated. Provided only to satisfy the Predicate interface; use matches(char) instead.
4	String collapseFrom(CharSequence sequence, char replacement)Returns a string copy of the input character sequence, with each group of consecutive characters that match this matcher replaced by a single replacement character.
5	int countIn(CharSequence sequence)Returns the number of matching characters found in a character sequence.
6	static CharMatcher forPredicate(Predicate<? super Character> predicate)Returns a matcher with identical behavior to the given Character-based predicate, but which operates on primitive char instances instead.
7	int indexIn(CharSequence sequence)Returns the index of the first matching character in a character sequence, or -1 if no matching character is present.

Create the following java program using any editor of your choice in say C:/> Guava.

Example

Following is the GuavaTester.java code −

import com.google.common.base.CharMatcher;
import com.google.common.base.Splitter;
public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testCharMatcher();
   }
   private void testCharMatcher() {
      System.out.println(CharMatcher.DIGIT.retainFrom("mahesh123")); // only the digits
      System.out.println(CharMatcher.WHITESPACE.trimAndCollapseFrom(" Mahesh Parashar ", ' '));
      // trim whitespace at ends, and replace/collapse whitespace into single spaces
      System.out.println(CharMatcher.JAVA_DIGIT.replaceFrom("mahesh123", "*"));
      // star out all digits                  
      System.out.println(CharMatcher.JAVA_DIGIT.or(CharMatcher.JAVA_LOWER_CASE).retainFrom("mahesh123"));
      // eliminate all characters that aren't digits or lowercase
   }
}

Compile the class using javac compiler as follows

C:\Guava>javac GuavaTester.java

Now run the GuavaTester to see the result −

C:\Guava>java GuavaTester

Output

This will produce the following output −

123
Mahesh Parashar
mahesh***
mahesh123