Understanding java-11.4 Regular Expressions from the beginning (2)-Basic syntax

In this section we will briefly describe the basic syntax of regular expressions.

Our goal is not to write the most complex expression, but to write an expression that completes the task.

1. Characters

Character	Significance
\ t	Tabs
\ n	Line break
\ r	Enter
\f	Page change
\e	Escape
\xhh	Hexadecimal
\uhhhh	Unicode hexadecimal

2. Character classes

Character class	Significance
.	Any character
[ABC]	Any character that contains ABC
[^ABC]	Any character that does not contain ABC
[A-za-z]	A-Z of uppercase and lowercase characters
[Abc[ijk]]	Same meaning as a|b|c|i|j|k (and set)
[A-z&&[ijk]]	Characters that contain only Ijk (intersection)
\s	whitespace (spaces, line breaks, page breaks, tab)
\s	Non-whitespace character [^\s]
\d	Digital
\d	Non-digital
\w	Word character [a-za-z0-9]
\w	Non-word characters

3. Boundary characters

Symbol	Significance
^	Begin
$	End
\b	The boundary of the word
\b	The boundaries of non-words
\g	Last match end

4. Logic processing

Xy	x followed by Y.
X| Y	X or Y
X	Capturing groups

5. Create a regular expression

Package Com.ray.ch11;public class Test {public static void main (string[] args) {string a = ' ddd012 '; for (string pattern: New string[] {"^[a-z]+[0-9]+$", "\\d+", "-?\\a+"}) {System.out.println (a.matches (pattern));}}}

Output:

True
False
False

Summary: This chapter mainly shows the simple syntax of regular expressions and how to create regular expressions in Java.

This chapter is here, thank you.

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Understanding java-11.4 Regular Expressions from the beginning (2)-Basic syntax