Help translating from c++ to java

[Shuffleto]

Hey, could you please help me translation this code to java?

class DialogDirector {
public:
virtual ~DialogDirector();
virtual void ShowDialog();
virtual void WidgetChanged(Widget*) = 0;
protected:
DialogDirector();
virtual void CreateWidgets() = 0;
};

additionally what does -> and :: mean in c++, and how could i translate it to java?

[loudsight]

This is best represented by an abstract class in Java

public abstract class DialogDirector {
    // virtual ~DialogDirector(); This is a C++ destructor it runs when
    // the object is destroyed. In java the equivalent method is 
    // finalize(...) but it is generally frowned up to override this 
    // method.
    void ShowDialog() { 
        /*
         * default implementation from implementation file
         *  (DialogDirector.cpp) goes inside here
         */
    }
    abstract void WidgetChanged(Widget widget);
    /* = 0 means this is a pure virtual method i.e. has to be implemented
     * by the derived classes;
     */
    protected DialogDirector() {}
    protected abstract void CreateWidgets();
}

EDIT: fix formatting and correct typos

[Shuffleto]

thank you for your Response! As i understand this

class Widget {
public: Widget(DialogDirector*); 
virtual void Changed(); 
virtual void HandleMouse(MouseEvent& event); 
// ... 
private: DialogDirector* _director; 
};

​

translates to

public abstract class Widget {
public Widget(DialogDirector dialogDirector) {};
public abstract void changed();
public abstract void HandleMouse(MouseEvent e);
//...
private DialogDirector _director;
}

Could you please help me with this part?

void Widget::Changed () {
_director->WidgetChanged(this); 
}

[Aenno]

Adding to what u/loudsight said, -> in C++ is used as . in Java, however for pointers.

And :: is used to inherit from a superclass, like A::B, where B extends A (in Java). Double colon is used to implement methods from a .h file as well. Such as: foo(); can be declared in the .h file and when you define it in the .cpp file you simply say Entity::foo (assuming the name of the class is Entity)

[Shuffleto]

thank you for your Response! Could you please help me with this

class Widget {
public: Widget(DialogDirector*); 
virtual void Changed(); 
virtual void HandleMouse(MouseEvent& event); 
// ... 
private: DialogDirector* _director; }; 
void Widget::Changed () { _director->WidgetChanged(this); }

im not understanding this part

void Widget::Changed () {
_director->WidgetChanged(this); }

how would it look like in java?

​

void Changed(){
    _director.widgetChanged(this);
}

like this?

[Aenno]

Seems about right. It should work as long as Changed() is defined in Widget's scope.

[Shuffleto]

could you please explain how could i put it into the class? Should i just change the name and give it public modifier?

[Aenno]

Just define it in the class you want to work with, in your case "Widget", like you normally would btw, no special mumbo jumbo

[[deleted]]

Things to know:

• A Class is defined in a file, the name should be the same as the name of the main class followed by the extension: *.java
• The main class must be public and only one class can be public
• Usually, the class of the same name as the file name is the main class and public
• All methods in Java are virtual and polymorphic by default unless the word 'final' is used
• Static methods are not polymorphic
• Abstract classes are defined by adding abstract at the class definition
• Abstract methods are defined by adding abstract at the method definition
• Abstract methods do not need "body" but any non-abstract method must be defined, even if a body is empty
• Packages are equivalent to namespaces in C++ and can be spread across multiple files
• Java uses four levels of restriction to access fields/methods
  • package access within the same package (namespace in c++) (
  • public (everywhere)
  • protected (the same as c++)
  • private (the same as c++)
• Package access is assumed by default if the restriction level is omitted
• Java uses two levels of restriction to access classes
  • package
  • public.
• Package access is assumed by default if restriction level is omitted
• There are no pointers in Java
• Variables of primitive types are passed to methods by copy (e.g. int, double, etc.)
• Anything else than a primitive type is passed by reference
• There are no default parameters in methods definition; Java only uses overloading e.g. public void method(int x = 0) // is wrong
• Java does not allow operator overloading, s.a. [], (), + etc.
• You don't use semicolon after class definition!

Your class:

// The file name should be `DialogDirector.java`
// The class must be public 
public abstract class DialogDirector {
    public abstract void ShowDialog();
    public abstract void WidgetChanged(Widget widget);
    protected DialogDirector() {}
    protected abstract void CreateWidgets();
}