This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
The array is made up of five variables that can refer to A objects. Each of these five variables is null when you construct the array. If you want five objects, then you must construct each one individually and add it to the array -- i.e.,
ob[i] = new A();
Note that rather than having exposed member variables and setting them after constructing an object, it's good practice to provide a constructor to initialize the members, i.e.,