What is a regex.Pattern class in Java?
A regular expression is a defined pattern used for matching and manipulating strings. In Java, there is a built-in API for regular expressions:
java.util.regex package
This package has three classes:
- Pattern class
- Matcher class
- PatternSyntax Exception class
A regular expression is not the property of one particular programming language; instead, it is supported by multiple languages.
Pattern class
The util.regex.Pattern is used for defining text patterns.
Some commonly used methods are:
| Methods | Description |
|---|---|
compile (String regex, int flags) |
It compiles the given expression into a pattern using the given flags. Flags are optional. |
flags() |
It returns the flags of the given expression. |
matcher(charSequence input) |
It creates the matcher that matches the input with the given expression. |
matches(String regex, CharSequence input) |
It compiles the regular expression and matches it against the input. |
pattern() |
It returns the regular expression from which the pattern is derived. |
split(CharSequence input) |
It splits the given pattern around the matches of the given input. |
toString() |
It returns the String of the given pattern. |
Code
// Pattern.matches() in Javaimport java.util.regex.Pattern;class Main{public static void main(String args[]){// The following statement prints true because// "Ah*" matches "Ahhhhhhhh"System.out.println (Pattern.matches("Ah*","Ahhhhhhhhh"));// The following statement prints false because// "Educative" matches "Educative Inc."System.out.println (Pattern.matches("Educative","Educative Inc"));}}
In the above code, the “*” symbol means that the character before it can repeat finitely at that position (e.g., hel*o is equivalent to hello).
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