Hangman | Help with the concept of obejcts as arguments

Question

I find it hard to understand how it works when we pass "game" as an argument when we create a new "Prompter-object".

I've really tried to follow the code, but I felt I needed to try with something simplier.

Let's say that we have a very simple calculator-program with 3 classes, which only does multiplication.

Main.java
Variables.java
Multiplication.java

How do I get to the variables in the "Variables-class" so I can use the multiplication-method in "Multiplication.java"? Any help is appreciated, but I would be superglad if someone could explain what it really means to create a object as an parameter and how we then work with it. Because I do understand the purpose of seperating the logic and practise, I just don't get how to achieve anything. Thanks!

* Variables.java
public class Variables {
                public int x;
                public int y;

// This constuctor sets the variables when it gets created
public Variables (int x, int y) {
        this.x = x;
        this.y = y;
    }

    public static void main(String[] args) {
         }
}

*Multiplication.java

public class Multiplication {

    public Variables variables;

    public Multiplication (Variables variables) {
        this.variables = variables;
    }
// The idea is that this method should use the varaibles in the other class to multiplicate
    public void multiplicate () {
        System.out.println(x * y);
    }

    public static void main(String[] args) {

    }
}

Main.java

public class Main {

public static void main(String[] args) {
            // Here we sets the variables with the constructor, 
    Variables variables = new Variables(5, 5);
            // Here we use the object as an parameter
    Multiplication multiplication = new Multiplication(variables);
            // So, how do I get to the variables x & y in "Variables.java"? 
    multiplication.multiplicate();

}

}

Answer 1 · 2016-09-10T15:39:52Z

September 10, 2016 3:39pm

First off,

    public static void main(String[] args) {

    }

You do not need another main method class.

Secondly,

    public void multiplicate () {
        System.out.println(x * y);
    }

You are saying that "what is x and y in the Multiplication class?", there is no x and y in the class because you did not create any. The variables from the Variable.class is not transferred to the Multiplication class, but since you did,

    public Multiplication (Variables variables) {
        this.variables = variables;
    }

you can ACCES the variables inside Variable.class.

So how do you access the variables in Variable.class? like this:

     void multiplicate () {
        System.out.println(variables.x * variables.y);
    }

This code is saying "Acces x inside variables class". This is called dot notation. I believe you have covered this in your previous course, but if you forgot, the dot notation is used to denote the hierarchy of the class.

Let me know if you have any more questions :)

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Björn Norén

Björn Norén

Hangman | Help with the concept of obejcts as arguments

1 Answer

Matthew Francis

Matthew Francis

Björn Norén

Björn Norén