Pattern compile(String,int) method in Java with Examples

31 Aug, 2021
The compile(String, int) method of the Pattern class used to create a pattern from the regular expression with the help of flags where both expression and flags are passed as parameters to the method. The Pattern class contains a list of flags (int constants) that can be helpful to make the Pattern matching behave in certain ways. For example, The flag name CASE_INSENSITIVE is used to ignore the case of the text at the time of matching.Syntax:  
public static Pattern compile(String regex, int flags)
Parameters: This method accepts two parameters:  
regex: This parameter represents the given regular expression compiled into a pattern.
flag: This parameter is an integer representing Match flags, a bit mask that may include CASE_INSENSITIVE, MULTILINE, DOTALL, UNICODE_CASE, CANON_EQ, UNIX_LINES, LITERAL, UNICODE_CHARACTER_CLASS and COMMENTS.
Return Value: This method returns the pattern compiled from passed regex and flags.Exception: This method throws following exceptions:  
PatternSyntaxException: This exception is raised if the expression’s syntax is invalid.
IllegalArgumentException: This exception is raised if bit values other than those corresponding to the defined match flags are set in flags.
Below programs illustrate the compile(String, int) 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 = "(.*)(for)(.*)?";         // create the string        // in which you want to search        String actualString            = "code of Machine";         // compile the regex to create pattern        // using compile() method        Pattern pattern = Pattern.compile(REGEX,                           Pattern.CASE_INSENSITIVE);         // check whether Regex string is        // found in actualString or not        boolean matches = pattern                              .matcher(actualString)                              .matches();         System.out.println("actualString "                           + "contains REGEX = "                           + matches);    }}
actualString contains REGEX = false
 
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 = ".*org.*";         // create the string        // in which you want to search        String actualString            = "geeksforgeeks.org";         // compile the regex to create pattern        // using compile() method        Pattern pattern = Pattern.compile(REGEX,                             Pattern.CASE_INSENSITIVE);         // check whether Regex string is        // found in actualString or not        boolean matches = pattern                              .matcher(actualString)                              .matches();         System.out.println("actualString "                           + "contains REGEX = "                           + matches);    }}
actualString contains REGEX = true
 
References: https://docs.oracle.com/javase/10/docs/api/java/util/regex/Pattern.html#compile(java.lang.String, int)
Akanksha_Rai
singghakshay
Java 8
Java-Functions
Java-Pattern
Java
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