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Enforcing a format on a string?
Alright, so let's say I have this string. I want to make it so that the string for this variable has to follow a certain format.
For example, "AAA-B", where the A's are a digit 0-9, the - is always in the same spot, and B is a letter but only from A-M. All of this for a single instance variable.
Is this possible? How could I go about doing this.
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Re: Enforcing a format on a string?
I would say that it's possible, but I don't understand how you'd apply it. You start off with, "let's say I have this string." What is the original content of the string you have? How is it decided what the string object you have will become in the format you've shown?
If you're asking how to generate a series like:
000-A through 000-M, then
001-A through 001-M, then
002-B through 002-M, then
etc.
It could definitely be done. You should make an effort to accomplish that and then come back when you need help.
Re: Enforcing a format on a string?
The string will be created based on user input, I'll ask them for them to enter it with a reminder of the format. However; as much as I can tell the user it has to be in that format, I need to create something so that if they entered it as AAA-C or AA-AC instead of AAA-B, it'll throw a custom exception (that I'm creating). The issue is that I just don't know how I can make it check to make sure A = Number 0-9, the - always at the index 3, and C = Character A-M, or else it'll throw my exception.
(Sorry if my descriptions or statements are a bit off, it's been a long tiring week already)
Re: Enforcing a format on a string?
Are you looking for a regexhow I can make it check to make sure A = Number 0-9, the - always at the index 3, and C = Character A-M
or can you code a loop or if to do the validation char by char?
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Re: Enforcing a format on a string?
I can code a loop/if to do the validation, mostly. I just worry with that because, if I were to do Character.isDigit at the index, wouldn't it throw my exception once it got to the - or the B, because it's not a digit?
And I have no idea about the limitations of what it can be (I.E. A-M) as I've never done or experienced that kind of problem..
Re: Enforcing a format on a string?
The code would look at each section of the String differently: 3 digits, one - and one letter
The validation might be done in a single if statement if the specific wrong char didn't need to be identified. No need for a loop.
If you don't understand my answer, don't ignore it, ask a question.
Re: Enforcing a format on a string?
So should I have 3 separate if statements? One for each of the things I'm checking? How could I go about doing this? (I haven't had much experience with this kind of issue until recently).
Re: Enforcing a format on a string?
Does the specific char that is wrong need to be reported
or is it enough to say there is an error in the String?
How many if statements to use depends on the response to the above.
If you don't understand my answer, don't ignore it, ask a question.
Re: Enforcing a format on a string?
It is enough to say that there is an error in the string. It shall throw an exception if there is that explains to the user the correct format that needs to be entered if they enter it wrongly formatted/with wrong numbers/letters (for ex "N"). It won't be reported where their error is.
Re: Enforcing a format on a string?
Ok, then a single if statement something like this:enough to say that there is an error in the stringif(firstCharIsOk && secondCharIsOk && continue with expressions to test each char to last char) { // String is OK }else { // String has bad character }
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Re: Enforcing a format on a string?
Right.
Here's what I have so far
if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") { status = false; } return status;
But I'm surely writing something wrong as I'm getting errors with it. Is it possible to do a isDigit test inside the charAt?
What should I do for the letters A-M check? I can't really make a comparison to see if the character is not N-Z right?
Re: Enforcing a format on a string?
Please copy the full text of the error messages and paste it here.I'm getting errors
Looks like you should read the API doc for the classes and methods you are using to see how to code them.
char values can be treated the same as int values. Use the < and > operators to test if a char is less than 'A' or greater than 'M' just like you would do with int variable you wanted to range check. The values for the chars don't have any undefined holes in the range of values. for example: 'A' + 1 = 'B' for all the lettersWhat should I do for the letters A-M check
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Re: Enforcing a format on a string?
The errors are:
Employee.java:105: error: ')' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: illegal start of expression if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: not a statement if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: ';' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: ')' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: illegal start of expression if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: not a statement if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: ';' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: ';' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ Employee.java:105: error: ';' expected if(num.charAt(0.isDigit()) && num.charAt(1.isDigit()) && num.charAt(2).isDigit()) && num.charAt(3) = "-") ^ 10 errors
Re: Enforcing a format on a string?
Read the rest of post#12
Note:
= is the assignment operator
== is the equality tester
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Re: Enforcing a format on a string?
Great, I got it. Thank you.
Re: Enforcing a format on a string?
Glad you got it working.
regex will probably also do what you want and I'm sure you will learn about regex later.
If you don't understand my answer, don't ignore it, ask a question.
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