This CASE_INSENSITIVE field of the Pattern class matches characters irrespective of case. When you use this as flag value to the compile() method and if you search for characters using regular expressions characters of both cases will be matched.
Note − By default, this flag matches only ASCII characters
Example 1
import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class CASE_INSENSITIVE_Example { public static void main( String args[] ) { Scanner sc = new Scanner(System.in); System.out.println("Enter input data: "); String input = sc.nextLine(); System.out.println("Enter required character: "); char ch = sc.next().toCharArray()[0]; //Regular expression to find the required character String regex = "["+ch+"]"; //Compiling the regular expression Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE); //Retrieving the matcher object Matcher matcher = pattern.matcher(input); int count =0; while (matcher.find()) { count++; } System.out.println("The letter "+ch+" occurred "+count+" times in the given text (irrespective of case)"); } }
Output
Enter input data: Tutorials Point originated from the idea that there exists a class of readers who respond better to online content and prefer to learn new skills at their own pace from the comforts of their drawing rooms. Enter required character: T The letter T occurred 20 times in the given text (irrespective of case)
Example 2
import java.util.Scanner; import java.util.regex.Matcher; import java.util.regex.Pattern; public class VerifyBoolean { public static void main(String args[]) { Scanner sc = new Scanner(System.in); System.out.println("Enter a string value: "); String str = sc.next(); Pattern pattern = Pattern.compile("true|false", Pattern.CASE_INSENSITIVE); Matcher matcher = pattern.matcher(str); if(matcher.matches()){ System.out.println("Given string is a boolean type"); } else { System.out.println("Given string is not a boolean type"); } } }
Output 1
Enter a string value: true Given string is a boolean type
Output 2
Enter a string value: false Given string is a boolean type
Output 3
Enter a string value: hello Given string is not a boolean type