How do I call this operation in my main? I'm using the visitor pattern. | Together Java | Page 1

wheat remnant Oct 21, 2023, 5:54 PM

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I followed a video to get this far but the person making the video never executed the pattern with a list so I have no clue how he called it and passed the list into the classes. Any help would be appreciated!

untold pierBOT Oct 21, 2023, 5:54 PM

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<@&987246399047479336> please have a look, thanks.

untold pierBOT Oct 21, 2023, 5:54 PM

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untold pier <@&987246399047479336> please have a look, thanks.

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to call the operation in your main using the visitor pattern with a list, you can follow these steps:

Create a visitor interface: Start by creating an interface that defines the operations that can be performed on different elements of the list. For example:

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public interface Visitor {
    void visit(ElementA element);
    void visit(ElementB element);
    // add more visit methods for other elements if needed
}

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Implement concrete visitors: Implement concrete visitor classes that implement the visitor interface and define how each operation is performed on different elements. For example:

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public class ConcreteVisitor implements Visitor {
    @Override
    public void visit(ElementA element) {
        // perform operation on ElementA
    }

    @Override
    public void visit(ElementB element) {
        // perform operation on ElementB
    }
}

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Create an element interface: Create an interface that represents the elements in your list and defines an accept method to accept visitors. For example:

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public interface Element {
    void accept(Visitor visitor);
}

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Implement concrete elements: Implement concrete classes for each element in your list that implement the element interface and define how to accept visitors. For example:

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public class ElementA implements Element {
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}

public class ElementB implements Element {
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}

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Create a list of elements: In your main method, create a list of elements that you want to apply the operation on. For example:

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List<Element> elements = new ArrayList<>();
elements.add(new ElementA());
elements.add(new ElementB());
// add more elements to the list if needed

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Apply the operation using visitors: Iterate over the list of elements and call the accept method on each element, passing the visitor as an argument. For example:

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Visitor visitor = new ConcreteVisitor();
for (Element element : elements) {
    element.accept(visitor);
}

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By following these steps, you can apply the operation defined in your visitor to each element in the list using the visitor pattern.

wheat remnant Oct 21, 2023, 5:56 PM

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Here is what i've tried but its giving me an error. The message is "The method printReports(ArrayList<FileBaseClass>) in the type PrintReports is not applicable for the arguments (FileListActions)"

golden aurora Oct 21, 2023, 5:57 PM

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wheat remnant Here is what i've tried but its giving me an error. The message is "The method p...

What's fileActList?

wheat remnant Oct 21, 2023, 5:58 PM

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its a class that I used to make the file array list.

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it has an addFile operation

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oh hang on

golden aurora Oct 21, 2023, 6:00 PM

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wheat remnant its a class that I used to make the file array list.

Show the code where you initialize fileActList.

wheat remnant Oct 21, 2023, 6:01 PM

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I messed up I thought that was a capital FileActList. That what i initialized heres the image.

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Sorry that my code is so poorly written in advance. Its pretty ugly.

golden aurora Oct 21, 2023, 6:04 PM

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wheat remnant I messed up I thought that was a capital FileActList. That what i initialized he...

Alright does the class FileListActions extends ArrayList<FileBaseClass>?

wheat remnant Oct 21, 2023, 6:04 PM

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no

golden aurora Oct 21, 2023, 6:05 PM

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then why are you using it as one in PrintReports#printReports?

wheat remnant Oct 21, 2023, 6:06 PM

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because thats where all my files are

golden aurora Oct 21, 2023, 6:06 PM

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you know about parameter types? you're making the parameter of the method up there type ArrayList<FileBassClass> but you're passing FileListActions instead

wheat remnant Oct 21, 2023, 6:09 PM

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Java is thoroughly confusing to me sorry. So scratch that. What way can I access my files that I saved into the ArrayList<FileBassClass> through my fileActList.addfile()?

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I wish I could show you all the code. I'm retrofitting this visitor pattern to my previous file storage program.

golden aurora Oct 21, 2023, 6:10 PM

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wheat remnant Java is thoroughly confusing to me sorry. So scratch that. What way can I access...

You haven't shown FileListActions so I can't know anything about it beside knowing it doesn't extend ArrayList<FileBaseClass>.

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Also I don't recommend learning design patterns before knowing how to create methods.

wheat remnant Oct 21, 2023, 6:12 PM

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true, kinda to late for that tho 🙂

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I'm stumped I don't know how to proceed. I feel as tho their is a better way to use this pattern within my code but I don't know java well enough to find it. Any tips?

golden aurora Oct 21, 2023, 6:17 PM

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wheat remnant true, kinda to late for that tho 🙂

Not really, you have to learn the alphabet before you can read a book. sure you can go into complex topic without having strong base but you'll struggle and eventually go to learn the fundamentals again

untold pierBOT Oct 21, 2023, 6:19 PM

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To create methods in Java, you need to follow these steps:

Step 1: Declare the Method

Start by specifying the access level (public, private, or protected) of the method.
Then specify the return type of the method. If the method does not return anything, use "void".
Next, provide a name for the method. Choose a descriptive name that reflects its purpose.
After that, include parentheses "()" after the method name to indicate that it is a method.
Finally, add curly braces "{}" to enclose the code block of the method.

Example:

public void printMessage() {
    // code block goes here
}

Step 2: Define Method Parameters (Optional)

If your method requires input values, you can define parameters inside the parentheses.
Parameters are variables that hold values passed to the method when it is called.
Specify the data type and a name for each parameter separated by commas.

Example:

public void printMessage(String message) {
    // code block goes here
}

Step 3: Implement Method Body

Inside the curly braces "{}", write the code that defines what your method should do.
You can include any valid Java statements and expressions within this code block.

Example:

public void printMessage(String message) {
    System.out.println(message);
}

Step 4: Call/Invoke the Method

To use a method, you need to call or invoke it from another part of your program.
Invoke a method by using its name followed by parentheses "()".
If there are parameters defined in the method declaration, pass appropriate values inside these parentheses.

Example:

printMessage("Hello World!");

That's it! You have successfully created and used a simple Java method. Methods allow you to encapsulate reusable blocks of code and make your program more modular and organized.

wheat remnant Oct 21, 2023, 6:20 PM

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I know how to make a method. I just don't know how to call this method and pass in my list.

golden aurora Oct 21, 2023, 6:23 PM

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wheat remnant I know how to make a method. I just don't know how to call this method and pass ...

I told you, you haven't sent FileListActions class so I have no clue.

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see how you're storing that in the FileListActions and make a method that returns it in ArrayList<FileBaseClass>

wheat remnant Oct 21, 2023, 6:24 PM

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When I try to pass it in I'm passing in an instance of the class FileListActions called fileListAct which is wrong and now I'm trying to figure out what I have to pass now.

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heres the pic

golden aurora Oct 21, 2023, 6:25 PM

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wheat remnant When I try to pass it in I'm passing in an instance of the class FileListActions...

You have to pass the files inside of FileListActions

wheat remnant Oct 21, 2023, 6:26 PM

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but that says it can't be resolved to a variable

golden aurora Oct 21, 2023, 6:26 PM

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Create a method that returns it and use it for the PrintReports#printReports method

golden aurora Oct 21, 2023, 6:27 PM

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wheat remnant but that says it can't be resolved to a variable

wdym?

wheat remnant Oct 21, 2023, 6:27 PM

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I subbed it in and got this. Did i misunderstand?

golden aurora Oct 21, 2023, 6:28 PM

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wheat remnant When I try to pass it in I'm passing in an instance of the class FileListActions...

also follow the camelCase when naming your methods or variables.

wheat remnant Oct 21, 2023, 6:28 PM

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sorry i was in a rush

golden aurora Oct 21, 2023, 6:29 PM

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wheat remnant I subbed it in and got this. Did i misunderstand?

where did you write this?

wheat remnant Oct 21, 2023, 6:29 PM

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main

golden aurora Oct 21, 2023, 6:30 PM

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so what's the files variable type in the main method?

wheat remnant Oct 21, 2023, 6:31 PM

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well I don't think there is one. I have the class instantiation but thats it.

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would that mean I need to call it perhaps within my FileListActions class so that it can pass files through

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I could make a operation in that class that calls the function in the visitor class and then passes it through

golden aurora Oct 21, 2023, 6:36 PM

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golden aurora Create a method that returns it and use it for the `PrintReports#printReports` m...

^

wheat remnant Oct 21, 2023, 6:37 PM

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ope

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i'm blind

#How do I call this operation in my main? I'm using the visitor pattern.