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Pattern compile() method in Java with Examples
The pattern class of the java.regex package is a compiled representation of a regular expression.
The compile() method of this class accepts a string value representing a regular expression and returns a Pattern object.
Example
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CompileExample {
public static void main( String args[] ) {
//Reading string value
Scanner sc = new Scanner(System.in);
System.out.println("Enter input string");
String input = sc.nextLine();
//Regular expression to find digits
String regex = "(\d)";
//Compiling the regular expression
Pattern pattern = Pattern.compile(regex);
//Printing the regular expression
System.out.println("Compiled regular expression: "+pattern.toString());
//Retrieving the matcher object
Matcher matcher = pattern.matcher(input);
//verifying whether match occurred
if(matcher.find()) {
System.out.println("Given String contains digits");
} else {
System.out.println("Given String does not contain digits");
}
}
}Output
Enter input string hello my id is 1120KKA Compiled regular expression: (\d) Given String contains digits
Another variant of this method accepts an integer value representing flags, where each flag specifies an optional condition, for example, CASE_INSENSITIVE ignores the case while compiling the regular expression.
Example
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CompileExample {
public static void main( String args[] ) {
//Compiling the regular expression
Pattern pattern = Pattern.compile("[t]", Pattern.CASE_INSENSITIVE);
//Retrieving the matcher object
Matcher matcher = pattern.matcher("Tutorialspoint");
int count = 0;
while(matcher.find()) {
count++;
}
System.out.println("Number of matches: "+count);
}
}Output
Enter input string Tutorialspoint Number of matches: 3
Updated on: 19-Nov-2019
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