How do you declare a class?

Answer 1

An instance of a class is also known as an object. In the Java language, you use the new operator. Here is an example:

Integer x; // Using the wrapper class, Integer. This doesn't create the object yet.

x = new Integer(5); // This will create the instance.

These commands can be combined into one:

Integer x = new Integer(5);

Answer 2

C++

Within your project, create a .hpp file. By this, I mean, using the name of class, create a new class.hpp file. A .hpp file is a header file, and contains a classes information.

So, if your class is called foobar, your .hpp file will be called foobar.hpp.

Within your new .hpp file, create a class in this manner:

FOOBAR.HPP

class foobar

{

public:

foobar();

~foobar();

private:

int variable;

}

This is the standard layout of a class, and every class you will create will look something like this.

There are two sections within the class that you'll notice; public and private. As the names suggest, everything within the public section can be accessed by anything, where as private data or functions can only be accessed within the class itself.

You'll notice some functions with the same name as your class name. foobar() is the class constructor. This function is called when the class is instantiated. Set up any class variables in here.

Second of all, you'll notice ~foobar();. This is the class destructor. This function is called when the class is destroyed. If you have dynamically allocated any memory, here is the place to delete it.

Once you've done this, create a corresponding .cpp file. So, in continuation, create a file called foobar.cpp.

Within this file, you'll need to implement the functions we've created in the .hpp:

FOOBAR.CPP

#include "foobar.hpp"

foobar::foobar()

{

//do something

}

foobar::~foobar()

{

//do something else

}

Within the .cpp file, we have included the .hpp file. The inclusion means, if any functions are used from the class, and if they're labelled properly (with a preficed foobar::) the compiler knows which functions is being referred to.

JAVA

In Java, classes are created in a similar way. The main differences are as follows:

• You don't use the term "#include". Instead, you use "import". The reason being that Java is a managed language, and is not native to the operating system. Java has an extensive number of libraries given to the programmer, and rather than having to get an external library like in C++, importing from what is given will suit most circumstances
• Class variables are not put in a section. Instead, if you want to label a variable private, you merely write private before it's declaration: for example private int hello;
• Variables can be given a value as they're declared

An example Java class:

class foobar

{

private int hello = 0;

private boolean exists = false;

public foobar()

{

//constructor of the class

}

}

Answer 3

public class ClassName

{

//member functions and data types go here

}