What is Validate.matchesPattern in Java?

How to import `Validate`

The definition of Validate can be found in the Apache Commons Lang package, which we can add to the Maven project by adding the following dependency to the pom.xml file:

<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.12.0</version>
</dependency>

For other versions of the commons-lang package, refer to the Maven Repository.

You can import the Validate class as follows:

import org.apache.commons.lang3.Validate;

Syntax

There are two possible variations of this method.

public static void matchesPattern(CharSequence input, String pattern, String message, Object... values)

// OR

public static void matchesPattern(CharSequence input, String pattern)

Parameters

input: The string to check.
pattern: The regular expression pattern to compare the string against.
message: The exception message to display if the message is not found.
values: The optional values for the formatted exception message.

Return value

This method does not return anything.

Code

import org.apache.commons.lang3.Validate;
public class Main{
    public static void main(String[] args){
        // Example 1
        String text = "helloeducative";
        String pattern = "[a-zA-Z]*";
        Validate.matchesPattern(text, pattern);
        // Example 2
        String exceptionMessageFormat = "The text '%s' is not matching the regex '%s'";
        text = "hello1234";
        pattern = "[a-zA-Z]*";
        Validate.matchesPattern(text, pattern, exceptionMessageFormat, text, pattern);
    }
}

Output

The output of the code will be as follows:

Exception in thread "main" java.lang.IllegalArgumentException: The text 'hello1234' is not matching the regex '[a-zA-Z]*'
	at org.apache.commons.lang3.Validate.matchesPattern(Validate.java:865)
	at Main.main(Main.java:15)

Explanation

Example 1

text= "helloeducative"
pattern = "[a-zA-Z]*"

Since the regex pattern matches the text, the method does not throw an exception.

Example 2

text = "hello1234"
pattern = "[a-zA-Z]*"

Since the regex pattern does not match the text, the method throws an IllegalArgumentException exception with "The text 'hello1234' is not matching the regex '[a-zA-Z]*'" as the exception message.

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