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Pattern compile(String) method in Java with Examples
  • Last Updated : 18 Feb, 2020

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 complied 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 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 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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