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 methodimport 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
Time Complexity : O(N)
Space Complexity : O(1)
Program 2:
Java
// Java program to demonstrate// Pattern.compile methodimport 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 = "neveropen.co.za"; // 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
Time Complexity : O(N)
Space Complexity : O(1)
References:
https://docs.oracle.com/javase/10/docs/api/java/util/regex/Pattern.html#compile(java.lang.String, int)