How can I access an object within another object's method?

Question

I am a (very) amateur Java programmer and I am having some trouble. Essentially, I have 2 classes: A and B, where B extends A.

In A, I have a method defined that creates some ZonedDateTime objects. I know how to create an instance of A in B so that I can execute A's method in B, but the problem lies later on when I need direct access to that method's ZonedDateTime objects. My first guess was to access them like this:

// Assuming the ZonedDateTime objects, e.g. dateTimeA, are within ClassA's "methodA()" method...
ClassA objectA = new ClassA();
System.out.println(objectA.methodA().dateTimeA);

When this inevitably errored, I figured I would need the method to return the objects, but from what I can tell, this is not possible; you can return only certain data types, not objects. I should also mention that I need the objects to remain as objects, so converting them to Strings then returning them that way is not going to work for me.

This issue feels very basic, but even so I couldn't find any answers elsewhere; I'm sorry if this is a duplicate question. Any help would be greatly appreciated.

EDIT(S):

Here is more of my code to make the problem more reproducible:

WatchFaceEDIT (i.e. A):

import java.time.ZonedDateTime;
import java.time.ZoneId;
    
public class WatchFaceEDIT {
    
    // Up here are some variable declarations and things used in the switch statement below.
    
    public void watchFaceMethod(String userInput) { // userInput is a parameter passed up from a subclass of this class.
        
        switch (userInput) {
            case "1":
            ZonedDateTime dateTimeHere = ZonedDateTime.now();
            hour = dateTimeHere.getHour();
            minute = dateTimeHere.getMinute();
            amPM = dateTimeHere.getHour();
            break;
            
            case "2":
            ZonedDateTime dateTimeThere = ZonedDateTime.now(ZoneId.of("Europe/Paris"));
            hour = dateTimeThere.getHour();
            minute = dateTimeThere.getMinute();
            amPM = dateTimeThere.getHour();
            break;
            
            case "3":
            hour = -1;
            minute = -1;
            break;
        }
        // The rest of the code in WatchFaceEDIT does some things with these hour and minute variables.
    }
}

WatchEDIT (i.e. B):

import java.time.format.DateTimeFormatter;

public class WatchEDIT extends WatchFaceEDIT {
    
    static void watchMethod(String userInput) {

        WatchFaceEDIT watchFaceObject = new WatchFaceEDIT();
        watchFaceObject.watchFaceMethod(userInput);

        DateTimeFormatter dateTimeFormat = DateTimeFormatter.ofPattern("hh:mm a 'on' EEEE, MMMM dd, yyyy");
        String dateTimeDisplay = watchFaceObject.watchFaceMethod(userInput).dateTimeHere.format(dateTimeFormat);
        // There is more to the code than this, but the problem seems to be here.
    }
}

I will briefly mention here that I thought the problem could have to do with the scope of the switch statement, but in WatchEDIT I was able to run watchFaceMethod without problems, and the method does utilize the created objects to display things.

It's hard to tell without an minimal reproducible example, but objectB.methodA().dateTimeA ought to work. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Jul 18, 2020 at 20:21
I am getting a void cannot be dereferenced error, but if I can't return the object in the method, I'm not sure how to fix this. Should I edit the question and include more of my actual code? I'm fairly new to StackOverflow, so excuse my ignorance. — kriegersan
– kriegersan, Commented Jul 18, 2020 at 20:25
Yes, post some code. If class B extends class A, you don't need a reference to an instance of A in B. B is a superclass of A. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Jul 18, 2020 at 20:33
You cannot access variables created within a method. A method can return values. You could make your variable class variables and add getter methods to return their values. — jnorman
– jnorman, Commented Jul 18, 2020 at 20:59

Nowhere Man · Accepted Answer · 2020-07-18 23:57:46Z

I checked your initial post to get more into the context and I'd suggest more suitable refactoring:

You should not use static for watchMethod in WatchEDIT - then you'll be able to refer members of its superclass
Move printing functionality in WatchFaceEDIT to separate method
Set all relevant values in WatchFaceEDIT::watchFaceMethod

That being said, the code fixes are as follows:

public class WatchFaceEDIT {
    // instance variables set inside watchFaceMethod
    protected int hour;
    protected int minute;
    protected int amPM;
    protected ZonedDateTime dateTimeObject;

    public void watchFaceMethod(String userInput) {
        
        switch (userInput) {
            case "1":
                dateTimeObject = ZonedDateTime.now();
                hour = dateTimeHere.getHour();
                minute = dateTimeHere.getMinute();
                amPM = dateTimeHere.getHour();
                break;
                
            case "2":
                dateTimeObject = ZonedDateTime.now(ZoneId.of("Europe/Paris"));
                hour = dateTimeThere.getHour();
                minute = dateTimeThere.getMinute();
                amPM = dateTimeThere.getHour();
                break;
                
            case "3":
                dateTimeObject = null;
                hour = -1;
                minute = -1;
                amPM = -1;
                break;
        }
        printSomething();
    }
    
    public void printSomething() {
        // move here the printing code from watchFaceMethod
        // if needed you may override this method in WatchEDIT class to modify display
        // The rest of the code in WatchFaceEDIT does some things with these hour and minute variables.
    }
}

public class WatchEDIT extends WatchFaceEDIT {
    
    public void watchMethod(String userInput) {
        // call method defined in super class and set instance variables
        watchFaceMethod(userInput);
        
        DateTimeFormatter dateTimeFormat = DateTimeFormatter.ofPattern("hh:mm a 'on' EEEE, MMMM dd, yyyy");
        
        String dateTimeDisplay = dateTimeObject == null ? "N/A" : dateTimeObject.format(dateTimeFormat);
        
        // There is more to the code than this, but the problem seems to be here.
    }
}

Main class just creating an instance of subclass

// does not need to extend WatchEDIT/WatchFaceEDIT classes
public class Main {
    public static void main(String[] args) {
        
        WatchEDIT watchObject = new WatchEDIT();

        System.out.println("Welcome to Interactive Watch!\n");
        System.out.println("What would you like to do?");
        System.out.println("[1] See local time.");
        System.out.println("[2] See local time in a particular place.");
        System.out.println("[3] See something special.\n");
        
        Scanner scannerObject = new Scanner(System.in);
        
        boolean loopBreak = true;
        
        while (loopBreak) {
            
            loopBreak = false; // loopBreak set to false
            
            String userInput = scannerObject.nextLine(); // User inputs some string
            
            switch(userInput) {
                case "1":
                case "2":
                case "3":
                    watchObject.watchMethod(userInput);
                    break;
                
                default:
                    loopBreak = true; // loopBreak set to true; while loop reinitiates
                    System.out.println("\nPlease enter a valid key.\n");
                    break;
            }
        }
    }
}

This ALMOST works. The problem is that watchFaceMethod actually displays some things on the CLI. When the method is called previously, it already displays what it needed to. Now it is getting called twice, and displaying the same thing twice.
Thanks for your help! I will continue working on it, but this has been valuable information.
You may check the answer I updated with regard to your initial post. Again, sorry if my previous comments sounded not so friendly. Good luck!
No worries. Due to some time constraints, I actually had to turn WatchFaceEDIT and WatchEDIT into a single class. I plan on looking at this project again in-depth in the future, though, to try and achieve what I am doing here when I have some more experience. This will be an excellent resource, so thank you very much for that.

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