You can use the private modifier to make an important improvement to the Queue class developed in the Try This 5-2 section of Chapter 5. In that version, all members of the Queue class use the default access, which is
basically public. In other words, it would be possible for a program that used Queue to directly access the underlying array, possibly accessing its elements out of order. Since the point of a queue is to provide a “first in, first out” list, it is not desirable to allow out-of-order access. Also
It would be possible for a malicious programmer to change the values ​​stored in the indexes putloc and getloc, thus tampering with the queue. Fortunately, these types of problems are easy to avoid by applying the private.

Purpose:
Improve the Queue class from the "Try This 5-2" section by applying the private access modifier to protect the internal members of the class.

Steps for Improvement:
Copy Original Class
Copy the original Queue class from the "Try This 5-2" section to a new file called Queue.java.

Apply private Modifier:
Add the private modifier to the internal members of the Queue class:

• The array q, which stores the elements of the queue.
• The putloc and getloc indexes, which manage insertion and removal operations in the queue.