How Do You Match Multiple Regex Patterns for a Single Line of Text in Java?
Lets Say I Have Multiple Patterns P1, P2, P3, , and So On. These Patterns Are Different Regex Patterns to Match Different Variations of Date. How Do I Match...
Lets say I have multiple patterns P1, P2, P3,, and so on. These patterns are different Regex patterns to match different variations of DATE.
How do I match these for the same input text most efficiently in a piece of code.
Of course, I can write a for() to loop over these patterns one by one, but is there a better way to do this?
5 Answers
I think you can use the | operator of the regex and put the different regexes in paranthesis to be considered one whole regex to be matched.
("(P1)|(P2)|(P3)")
To complement the other answers...
You can write one big, hard-to-read pattern using the alternation operator:
r1|r2|r3|...|rn
where r1 etc are themselves "fully-fleged" regexes.
However you have to be careful about the order of alternations: the first to match wins. That is, if the regex engine is not a POSIX regex engine but java.util.regex's engine isn't.
Therefore, with text catflap, using regex:
cat|catflap
Java will match cat; a POSIX regex engine will match catflap (the longest, leftmost match).
Sticking with more individual, maintainable patterns is imho a better option.
You can use alternation (|) operator to combine multiple patterns for your regexp.
But in case you have various input and you will have to convert them to instance of Date from a string. Then you must follow in a sequence and validate the input one by one. So single regexp may validate the input but it could not be used to any other logic.
I had a similar problem. Having all the patterns in a single pattern and separating the patterns by | worked for me '((P1)|(P2)|(P3))'
My code for ref:
input_text = '''Carlisle Farm Specialist F-1 Farm Tire - 12.5L-15 LRF/12 ply (Wheel
Not Included)
Evergreen EU72 205/50ZR16 OWL87W RT-5 Truck tire
Goodyear Marathon Trailer Tire w/Galvanized Rim ST215/75R14 LRC (5 Lug On 4.5)
1 X New Achilles \"ATR Sport\" 265/35ZR18 97W XL High Performance Tires 265/35/18
Set of 2 ZEEMAX Heavy Duty All Steel ST235/85R16-14PR TL Trailer Tire - 11073
1 X New Lexani LXHT-106 LT285/70R17/8 118Q BW All Season Performance SUV Tires
1 X New Nankang N889 Mudstar M/T LT245/75R16 120/116N E/10 Ply ROWL Mud Tires MT
Pirelli Night Dragon Motorcycle Front Tire 130/90-16 2211500'''
#(Extract : 12.5L-15 LRF/12)
#(Extract : 205/50ZR16 OWL87W)
#(Extract : 265/35ZR18 97W XL)
#(Extract : 130/90-16 )
#(Extract : ST215/75R14 )
#(Extract : ST235/85R16-14PR TL)
#(Extract : LT285/70R17/8 118Q BW)
#(Extract : LT245/75R16 120/116N E/10)
pattern = re.compile(r'(([A-Z][A-Z]\d\d\d/\d\d\D\d\d(.[0-9]......([A-Z].([A-
Z]...)?)?)?)|(\d\d\d/\d\d\D\D?\d\d\s\b(\w\w\w.\w[A-Z])?)|(\d\d\.............))')
I would not use Patterns to match dates.
You have DateFormat and SimpleDateFormat classes to do so.
This said, combining Patterns can be done with the alternation (|) operator on the String representation of the Pattern.
Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.
