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How to use regular expression in Java to pattern match?
A regular expression is a string of characters that defines/forms a pattern to search an input text. A regular expression may contain one or more characters, using a regular expression you can search or replace a string.
Java provides the java.util.regex package for pattern matching with regular expressions. The pattern class of this package is a compiled representation of a regular expression. To match a regular expression with a String this class provides two methods namely −
- compile(): This method accepts a String representing a regular expression and returns an object of the Pattern object.
- matcher(): This method accepts a String value and creates a matcher object which matches the given String to the pattern represented by the current pattern object.
Example
Following Java program accepts a string from the user, verifies whether it contains alphabet (both cases), It also accepts digits.
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Test {
public static void main( String args[] ) {
String regex = "[a-zA-Z][0-9]?";
Scanner sc = new Scanner(System.in);
System.out.println("Enter an input string: ");
String input = sc.nextLine();
//Creating a Pattern object
Pattern p = Pattern.compile(regex);
//Creating a Matcher object
Matcher m = p.matcher(input);
if(m.find()) {
System.out.println("Match occurred");
}else {
System.out.println("Match not occurred");
}
}
}Output 1
Enter an input string: sample text Match occurred
Output 2
Enter an input string: sample text 34 56 Match occurred
Updated on: 05-Feb-2021
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