How do you match multiple Regex patterns for a single line of text in Java?

Question

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

Answer 1

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.

Answer 2

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\.............))')

Answer 3

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)")

Answer 4

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.

Answer 5

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.