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Pattern compile(String) method in Java with Examples

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  • Difficulty Level : Expert
  • Last Updated : 31 Aug, 2021

The compile(String) method of the Pattern class in Java is used to create a pattern from the regular expression passed as parameter to method. Whenever you need to match a text against a regular expression pattern more than one time, create a Pattern instance using the Pattern.compile() method.
Syntax: 

public static Pattern compile(String regex)

Parameters: This method accepts one single parameter regex which represents the given regular expression compiled into a pattern.
Return Value: This method returns the pattern compiled from the regex passed to the method as a parameter.
Exception: This method throws following exception:  

  • PatternSyntaxException: This exception is thrown if the expression’s syntax is invalid.

Below programs illustrate the compile(String) method: 
Program 1:  

Java




// Java program to demonstrate
// Pattern.compile() method
 
import java.util.regex.*;
 
public class GFG {
    public static void main(String[] args)
    {
        // create a REGEX String
        String REGEX = ".*www.*";
 
        // creare the string
        // in which you want to search
        String actualString
            = "www.geeksforgeeks.org";
 
        // compile the regex to create pattern
        // using compile() method
        Pattern pattern = Pattern.compile(REGEX);
 
        // get a matcher object from pattern
        Matcher matcher = pattern.matcher(actualString);
 
        // check whether Regex string is
        // found in actualString or not
        boolean matches = matcher.matches();
 
        System.out.println("actualString "
                           + "contains REGEX = "
                           + matches);
    }
}


Output: 

actualString contains REGEX = true

 

Program 2: 

Java




// Java program to demonstrate
// Pattern.compile method
 
import java.util.regex.*;
 
public class GFG {
    public static void main(String[] args)
    {
        // create a REGEX String
        String REGEX = "brave";
 
        // creare the string
        // in which you want to search
        String actualString
            = "Cat is cute";
 
        // compile the regex to create pattern
        // using compile() method
        Pattern pattern = Pattern.compile(REGEX);
 
        // check whether Regex string is
        // found in actualString or not
        boolean matches = pattern
                              .matcher(actualString)
                              .matches();
 
        System.out.println("actualString "
                           + "contains REGEX = "
                           + matches);
    }
}


Output: 

actualString contains REGEX = false

 

Reference: https://docs.oracle.com/javase/10/docs/api/java/util/regex/Pattern.html#compile(java.lang.String)


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