你应该知道的10个java 正则表达式详解
正则表达式是编程的艺术,但正则表达式,不容易调试,也不好学习,但他强大的功能吸引了很多的开发者去使用正则表达式,本文总结了10个非常实用的正则表达式,并配备了详细的解释,这也是最好学习正则表达式的方法。
本文主要详细介绍如下正则表达式:
1. 用户名正则表达式
2. 密码正则表达式
3. 16进制颜色正则表达式
4. email 正则表达式
5. 文件扩展名 正则表达式
6. IP地址正则表达式
7. 时间正则表达式
8. 日期正则表达式
9. HTML 正则表达式
10. 超级链接正则表达式
1. 用户名正则表达式
^[a-z0-9_-]{3,15}$
^ # Start of the line [a-z0-9_-] # Match characters and symbols in the list, a-z, 0-9 , underscore , hyphen {3,15} # Length at least 3 characters and maximum length of 15 $ # End of the line
2. 密码正则表达式
((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,20})
( # Start of group (?=.*\d) # must contains one digit from 0-9 (?=.*[a-z]) # must contains one lowercase characters (?=.*[A-Z]) # must contains one uppercase characters (?=.*[@#$%]) # must contains one special symbols in the list "@#$%" . # match anything with previous condition checking {6,20} # length at least 6 characters and maximum of 20 ) # End of group
3. 16进制颜色正则表达式
^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$
^ #start of the line # # must constains a "#" symbols ( # start of group #1 [A-Fa-f0-9]{6} # any strings in the list, with length of 6 | # ..or [A-Fa-f0-9]{3} # any strings in the list, with length of 3 ) # end of group #1 $ #end of the line
4. email 正则表达式
^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+ (\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$
^ #start of the line [_A-Za-z0-9-]+ # must start with string in the bracket [ ], must contains one or more (+) ( # start of group #1 \\.[_A-Za-z0-9-]+ # follow by a dot "." and string in the bracket [ ], must contains one or more (+) )* # end of group #1, this group is optional (*) @ # must contains a "@" symbol [A-Za-z0-9]+ # follow by string in the bracket [ ], must contains one or more (+) ( # start of group #2 - first level TLD checking \\.[A-Za-z0-9]+ # follow by a dot "." and string in the bracket [ ], must contains one or more (+) )* # end of group #2, this group is optional (*) ( # start of group #3 - second level TLD checking \\.[A-Za-z]{2,} # follow by a dot "." and string in the bracket [ ], with minimum length of 2 ) # end of group #3 $ #end of the line
5. 文件扩展名 正则表达式
([^\s]+(\.(?i)(jpg|png|gif|bmp))$)
( #Start of the group #1 [^\s]+ # must contains one or more anything (except white space) ( # start of the group #2 \. # follow by a dot "." (?i) # ignore the case sensitive checking ( # start of the group #3 jpg # contains characters "jpg" | # ..or png # contains characters "png" | # ..or gif # contains characters "gif" | # ..or bmp # contains characters "bmp" ) # end of the group #3 ) # end of the group #2 $ # end of the string ) #end of the group #1
6. IP地址正则表达式
^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\. ([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$
^ #start of the line ( # start of group #1 [01]?\\d\\d? # Can be one or two digits. If three digits appear, it must start either 0 or 1 # e.g ([0-9], [0-9][0-9],[0-1][0-9][0-9]) | # ...or 2[0-4]\\d # start with 2, follow by 0-4 and end with any digit (2[0-4][0-9]) | # ...or 25[0-5] # start with 2, follow by 5 and end with 0-5 (25[0-5]) ) # end of group #2 \. # follow by a dot "." .... # repeat with 3 time (3x) $ #end of the line
7. 时间正则表达式
12 小时制正则表达式 (1[012]|[1-9]):[0-5][0-9](\\s)?(?i)(am|pm)
( #start of group #1 1[012] # start with 10, 11, 12 | # or [1-9] # start with 1,2,...9 ) #end of group #1 : # follow by a semi colon (:) [0-5][0-9] # follow by 0..5 and 0..9, which means 00 to 59 (\\s)? # follow by a white space (optional) (?i) # next checking is case insensitive (am|pm) # follow by am or pm
24 小时制正则表达式 ([01]?[0-9]|2[0-3]):[0-5][0-9]
( #start of group #1 [01]?[0-9] # start with 0-9,1-9,00-09,10-19 | # or 2[0-3] # start with 20-23 ) #end of group #1 : # follow by a semi colon (:) [0-5][0-9] # follow by 0..5 and 0..9, which means 00 to 59
8. 日期正则表达式
(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)
( #start of group #1 0?[1-9] # 01-09 or 1-9 | # ..or [12][0-9] # 10-19 or 20-29 | # ..or 3[01] # 30, 31 ) #end of group #1 / # follow by a "/" ( # start of group #2 0?[1-9] # 01-09 or 1-9 | # ..or 1[012] # 10,11,12 ) # end of group #2 / # follow by a "/" ( # start of group #3 (19|20)\\d\\d # 19[0-9][0-9] or 20[0-9][0-9] ) # end of group #3
9. HTML 正则表达式
<("[^"]*"|'[^']*'|[^'">])*>
< #start with opening tag "<" ( # start of group #1 "[^"]*" # only two double quotes are allow - "string" | # ..or '[^']*' # only two single quotes are allow - 'string' | # ..or [^'">] # cant contains one single quotes, double quotes and ">" ) # end of group #1 * # 0 or more > #end with closing tag ">"
10. 超级链接正则表达式
(?i)]+)>(.+?)
( #start of group #1 ?i # all checking are case insensive ) #end of group #1 ]+ # anything except (">"), at least one character ) # end of group #2 > # follow by ">" (.+?) # match anything # end with "
提取超级链接正则表达式
\s* #can start with whitespace (?i) # all checking are case insensive href # follow by "href" word \s*=\s* # allows spaces on either side of the equal sign, ( # start of group #1 "([^"]*") # only two double quotes are allow - "string" | # ..or '[^']*' # only two single quotes are allow - 'string' | # ..or ([^'">]+) # cant contains one single / double quotes and ">" ) # end of group #1
有一点正则表达式的基础,然后通过这些正则表达式,慢慢分析,可以得到一般正则表达式的写法,而且可以学会很多规则,正则表达式的熟悉过程是个长期使用的过程。