Java and regular expressions

1. The use of regular expressions:

1. Typical usage:

//Compile a string into a Pattern object

Pattern p = Pattern.compile("a*b");

//Use Pattern Object creates Matcher object

Matcher m = p.matcher("aaaaab");

boolean b = m.matches();//Return true

2. Simple usage

The Pattern object defined above can be reused, If a regular expression only needs to be used once, you can directly use the static method matchers() of the Pattern class.

This method automatically compiles the specified string into an anonymous Pattern object and performs matching:

boolean b = Pattern .matches("a*b","aaaaab");//Return true

3. Tips

Pattern is an immutable class and can be used safely by multiple concurrent threads.

Common methods of the Matcher class:

find(): Returns whether the target string contains a substring matching Pattern.

group(): Returns the last substring matching Pattern.

matches(): Returns whether the entire target string matches Pattern.

start(): Returns the starting position of the last substring that matched Pattern in the target string.

end(): Returns the end position of the last substring matching Pattern in the target string plus 1.

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