Creating a Pattern object

Create a Pattern object using a factory method, compile() of the Pattern class. This is a static method, so you invoke it using the class, not an object:

Pattern pat = Pattern.compile( "x+y+");

A factory method (such as compile()) is a static method of a class that creates an object. It is like a constructor, but is not used with the new operator. It has a name other than the class name. Here are the two ways to call compile():

public static Pattern compile(String regex)

Creates a Pattern object based on the regular expression in regex. It throws a PatternSyntaxException if the expression's syntax is invalid.

public static Pattern compile(String regex, int flags)

Creates a Pattern object based on the regular expression in regex. Various options are chosen by setting various bits in flags. It throws a PatternSyntaxException if the expression's syntax is invalid. It throws a IllegalArgumentException if flags is invalid.

Details about the flags and the exceptions are discussed below. For now, assume that the program will halt (and produce a stack trace) if the expression or the flags are incorrect.