如何从另一个类java调用带有参数的方法作为对象？

Question

I am trying NOT to just call the method by inputting the values manually, but to run a method of another class from another class. I tried to find out the solution by looking at the similar questions but they did not help me in this context.

I might be wrong please forgive me, but this requirement is asking me to call a method with parameters, which I do not understand how to do.

This is the requirement:

a) Add a method payForHoliday() to the Member class. This method will simply call a method in the Website class to pay for the holiday (ie to record the transaction with the website). And here we have a problem because the object from the Member class doesn't keep a record of which website the member is logged into.

Class Website :

public class Website {
    private String websiteName;
    private double salesTotal;
    
    public Website(String newWebsiteName)
    {
        websiteName = newWebsiteName;
    }

    // lines omitted

    public void checkout(Member purchase, Holiday chosen) 
    {
        if (checkHitDiscount() == true)
        {
            System.out.println("Congrtulations you are eligible for 10% discount!");
            salesTotal = chosen.price;
        }
        else
        {
            System.out.println("successful completion of the transaction");
            salesTotal = chosen.price;
        }
    }

Class Member :

public class Member {
    private String email;
    public int membershipNumber;
    Holiday holiday;
    Website website;

    public Member(String newEmail, int newMembershipNumber)
    {
        email = newEmail;
        membershipNumber = newMembershipNumber;
    }

    // lines omitted

    public void payForHoliday(Member purchase, Holiday chosen) 
    {
         // This method needs to run the "checkout()" method in Website class
    }

Answer 1

Before you can execute a (non-static) member of another class, you need an object that is an instance of that class.

To say it another way, your checkout method is an operation that operates on a particular Website, by virtue of it being defined as a member of the Website class.

Therefore, to call it you need

    Website xyz = …. something that delivers a website …;

and then you can call

    xyz.checkout(…);

The "something that delivers a website" is whatever fits in with your application design. Maybe it's as simple as 'new Website()', but it's not possible to tell without knowing what else a Website actually represents in your design.

---

You are missing details of how this is supposed to work. I will supply some guesses. Firstly, I assume that there are more members that web sites, that is, that each possible web site has more than one member.

That means that there needs to be a way to hook up a member to a web site. The requirements point this out as a 'problem' - we can infer that you're supposed to solve the problem.

One way would be for the Member constructor to tell you the Website:

public Member(String newEmail, int newMembershipNumber, Website newSite)
{
    email = newEmail;
    membershipNumber = newMembershipNumber;
    website = newSite;
}

then you can do this:

public void payForHoliday(Member purchase, Holiday chosen) 
{
     website.checkout(purchase, chosen);
}

but that doesn't make a lot of sense to me - why does this method need a 'Member' argument that is different to the Member that contains it? Are you sure you've got that detail right? This is more plausible:

public void payForHoliday(Holiday chosen) 
{
     website.checkout(this, chosen); // 'this' means the current Member
}

But whether that's the approach that is intended or not, we can't say, because there is insufficient detail in the question. How are any of these things used? What creates Members? Is the code that creates Members aware of the particular Website it is making a member for?

Answer 2

The problem was that I was trying to add an object of the same class Member to call the method from the other class Website , which had a Member purchase as a parameter.

So in order to correctly call that method, I used this code:

    public void payForHoliday(Holiday test) 
    {
       website.checkout(this, test);
    }

• For pointing to the method checkout() in the Website class, I used an address (Website website) declared as an instance variable in Member class.

• The this keyword tells the program that the parameter is the object itself, which is calling The method.

• The test variable is placed as a parameter due to the fact that is a pointer from another class. (I changed the variable name to another name to avoid conflicts with the one in the checkout() method)