Thread: How to define a string pattern using variables?

Hi guys

Firstly Happy new year to you soon, can someone please tell me this:

I understand how to write a pattern with single character of regular-expression (eg. [a-zA-Z]), but how to define the pattern with my own varibles?

Eg. I got 3 variables

String roadName, city, cityDistance;

, how to define below string using my own variables?

<roadName> <cityA> <AB distance> <cityB> [<BC distance> <cityC> […]]

Many Thanks

You can concatenate Strings whether they are stored as String variables or as literals. Try using the + operator or using a StringBuilder.

When coming up with a regular expression, it oftentimes helps to write out the rules in English first. What exactly is the form? Is it "any String followed by a number followed by any String", or does white space count, or are numbers even required, or is there anything else you want to take into consideration? What kinds of things do you NOT want the pattern to accept?

What would be an acceptable file you would need to parse (or ones your program should be able to recognize errors in and handle them gracefully)? Sometimes regular expression are over-kill and make the problem too hard.

For example, if the file contains all the cities connected to a particular road, and then the distance between cities by taking that road all on a single line (or separated by some special character) then you could simply hard-code a Scanner object to read in items, determine what your current state is (are you looking at/for a road, a city, or a distance?), then mark that object as such.

Originally Posted by ice

Thanks KevinWorkman, I didn't express my question well, I mean how to write a general pattern for a given string with string variables. For example:
Here are some strings, each string represent one road name:

"OR Adelaide 300 Melbourne"
"HH Melbourne 850 WestSydney 105 Sydney"
"BushTrack Adelaide 2448 Brisbane"
....

Obviously they have similar form, how do I write just one pattern in java that can represent any of above road?

Thanks heaps

Sometimes regex is not the right tool for the job. Where does you strings come from ? a text file?