wide solar
First of all i am new here so if I document anything wrong, please forgive me.
Problem:
I want to create a program. This Program should create a List which gets the name of the of the value of the "userInput" String which is the input of the user.
For Example -> user gets asked for input and gives Input like, "listOne" so the List should get the name "listOne"
Thanks
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fiery eagle
First of all i am new here so if I document anything wrong, please forgive me.
P...
The name of the variable doesn't really matter. What you want to do is add the userInput value to the list
wide solar
The name of the variable doesn't really matter. What you want to do is add the u...
when I am creating the list in line 14 I get the error, that the name is duplicate, because it is already used in line 9, when I am saving the input that the user gives me.
My problem is that I want to name the list after the value that the user gives me in line 9. Not adding the value the user gives me to the list.
fiery eagle
Give the list another name
And the name of the list doesn't matter
Well it should be descriptive of what the list contains
But you shouldn't name a variable after user input
wide solar
ok i get your point. But I want to create a program which can create ArrayLists as soon a the user wants it. So that this process is automated and in this case is there any other approach, because the list that gets created automatically needs to get a name
should have described my whole plan right away
@fiery eagle
fiery eagle
All you need to do is put user input and access it at a later time
remote raptor
you cannot use a String as the name of a variable
variable names can only be specified directly
marble totem
(unless you're up for using bytecode manipulation, but you generally never need to rename a variable)
wide solar
Ok, and how do I define the variable name when it should get created automatically?
is there any way to do this?
ivory scroll
you choose one
the value gets created dynamically. the variable does not
your program creates the list when the user wants to, not the variable
wide solar
you choose one
but if I have to chose it, isnt it pretty static then?
sorry if I ask a lot, I dont know how long you normally discuss on a problem.
I really want to understand it 100%
ivory scroll
the name is static, the variable is not
a variable declaration says, when the variable is created, the variable should have name x
a local variable gets created dynamically, whenever the declaration is reached
wide solar
a variable declaration says, *when* the variable is created, the variable should...
so I name the ArrayList static, and then?
i dont get the second part
ivory scroll
there is no second part
ivory scroll
and if the user decides to create another list?
it gets put in the "same" variable. local variables are discarded when they go out of scope, ie where they can be accessed from
a variable defined as a function parameter can only be accessed inside that function, a variable defined inside a loop can only be used inside that loop
if you don't store it somewhere else, the first arraylist is just lost along with the variable
think of function parameters like i mentioned, they're created dynamically each time you call the function, with the same name each time
wide solar
ok that helped me a lot with my understanding of scopes
is there a way to create an ArrayList with a function for example. which gets a name assigned and not hard coded?
ivory scroll
no, and it's not useful to do so at all
wide solar
ah alright
ivory scroll
also you don't assign names to the list
you assign names to where the list goes
you can achieve dynamic "naming" with a map, but that's not particularly useful in this case either
wide solar
good to know, i am kind of new to java
ivory scroll
actually might be depending on what you actually need to do, you weren't very clear on that
but dynamic naming on variables isn't useful.
ivory scroll
don't think that'll be necessary
do you need to persistently store the arraylist along with the given name
for other uses in your program later
wide solar
I want to create a program which can be used by anyone.
They should be able to create a List, for example a shopping list.
And be able to create another List, for example workout plan
like a small "to do" program
cosmic bough
and those lists should be saved and read back into the program later, right?
wide solar
later i wanted to implement a GUI
ivory scroll
do you need to persistently store the arraylist along with the given name
so yes, is what im gathering
....i asked a yes/no question, because that's all the info i need
wide solar
and those lists should be saved and read back into the program later, right?
yes, but i wanted to automate the creation of the list to begin with
ivory scroll
you'll want a map for that, not variables.
wide solar
do you need to persistently store the arraylist along with the given name
yes, thats the next step
ivory scroll
yes, but i wanted to automate the creation of the list to begin with
i don't think you're using "automate" correctly here
wide solar
you'll want a map for that, not variables.
ok, maps noted
ivory scroll
cosmic bough
yes, but i wanted to automate the creation of the list to begin with
well you have the list you want to store the items in already, you created the variable that will hold the items. next, you just need to ask the user what items to put into the list, process the input and add it
wide solar
my idea would have been to create a function which can be called and then creates a list
problem would have been, when the function gets called a second time
because the name would be duplicated
is my understanding correct, that this would not work?
because you know the name is hard coded
wide solar
well you have the list you want to store the items in already, you created the v...
i already tried it out and it worked
my problem was just that i had the idea that i just described
ivory scroll
because you know the name is hard coded
there's no issue with that
variable names just do not matter to the runtime
they generally don't matter to the user, either
they only really matter to the developer
cosmic bough
variable names just do not matter to the runtime
in fact, variable names get completely tucked away at runtime, you can completely delete them from the compiled program and it will still run
they only exist in the compiled program to make debugging easier