Thread: Error - Going from Java to C++

In C++ there are pointers (welcome to the Darkside)

Code:

class CarNode: public Car {
  public:
    Car *carObject;
    CarNode *next;

    CarNode(Car *newCar, CarNode *newNext) {
      carObject = newCar;
      next = newNext;
  }
}

Code:

#include <list>

...

std::list<Car> cars;

Originally Posted by C_ntua

In C++ there are pointers (welcome to the Darkside)

In Java, everything is references. And references is just another name for pointers, because they behave exactly the same without the C syntax (which just makes them even more powerful).
So I would say welcome back from the Dark Side. Java is Evil™. And their references are just plain stupid and pathetic.
Welcome to C++, where everything does NOT have to be references or pointers.

Java's references are all safe and colourful with flowers and sunshines. They are Good.
C++ pointers are more powerful and more dangerous. They are Evil.

Java is just more simplistic. Can agree on the pathetic, but not on the stupid.

(To the point, they are the similar. So everywhere you have references in Java you will have to use pointers in C++. Somethings would be done differently probably in C++, so an exact translation is not the optimized solution)

Originally Posted by C_ntua

Java's references are all safe and colourful with flowers and sunshines. They are Good.
C++ pointers are more powerful and more dangerous. They are Evil.

I doubt that very much.
They are not all colorful. Comparing two objects will compare their two references which is NOT what you would expect, for example. Is there a way to compare them, then? NO, because there is NO way to dereference the references. Instead, we must rely on C-ish ways of member functions for such stuff.

C++'s pointers are a tool which complements other things in the language. The fact that you can point a pointer to an array and copy bytes to the beginning of a pointer are examples of what is dangerous, but that is not the default of the pointers, but other mechanics of the language.

Plus you still have NULL pointer exceptions in Java just like you do in C++, so I don't see how that's much safer. The only thing that's safer is that Java has garbage collection which reduces the chances of memory leaks.

First of all C++ classes end in ;.

Second the code can also be written like this:

Code:

class CarNode: public Car {
  public:
    Car & carObject;
    CarNode &next;

    CarNode(Car &newCar, CarNode &newNext) {
      carObject = newCar;
      next = newNext;
  }
};

This makes it so that you cannot change what carObject and next point to, and that you cannot set them to NULL. Since this looks like a linked list implementation, this may not be what you want, but it's worth pointing out the alternative as it can be applied to other situations, and is generally prefered when it fits. Here you are using C++ references

Third, this thead is horrible for explaining the differences between java pointers, and C++ pointers and references. You need a C++ book. In general though, C++ pointers are more powerful, because you can have pointers and references to primitive types. However, unlike java, you have to make sure that you don't try to dereference a NULL pointer, as it will lead to unpredictable results. (Java will just show you an error and close the program in a controlled mannor, or do whatever other beahior you specify).