Style problems aside, there are (at least) three problems with this code:

1. In the second for loop, the variable i is undefined.  If you're using an
old C++ compiler this may compile, but with a newer, more
standards-compliant compiler it won.t  You need to declare a new loop
variable for the second loop - the 'i' from the fist loop is gone.

for (int i = 0...

2. You never allocated any memory for an array, so assuming you fix the
for-loop scoping problem, the code will likely crash at runtime.

3. You used std::endl without #include-ing <iomanip>.

Here's a revised version to point you in the right direction:

#include <iostream>
#include <iomanip>

using namespace std;

class Array
{
private:
 int* m_item;
 int  m_capacity;

public:
 Array(int cap)
   : m_capacity(cap),
     m_item(new int[cap])
 {
 }

 int& operator[](int index)
 {
   return m_item[index];
 }

 int capacity() const
 {
   return m_capacity;
 }
};

int main()
{
 Array Jan(5);

 for (int i =0; i<5; i++)
   Jan[i] = i;

 for(int i =0; i<5; i++)
   cout << Jan[i] << endl;

 return 0;
}

-cd