The municipality needs a system to handle the queues at their offices. At the counter, persons in need of documents from the offices can get a unique, progressive number that defines their position in the queue. The requests are handled according to this number.

Part 1. Realize a class Request with the following attributes:

• the name of the person that issued the request (a string);
• the requests's progressive number (an integer).

• a constructor to create a new request, given a person's name and a progressive number;
• getPerson that returns the person's name;
• getNumber that returns the progressive number;
• returning a String representation of a request object, by overriding the toString method of Object.

Solution: skeleton of the class, class Request

Part 2. Realize a class Counter, each of whose objects stores a queue of requests issued at the counter. The class should export the following functionalities:

• a constructor to create an empty counter, that is a counter with an empty queue;
• addRequest that, given a person's name appends a new request to the counter's queue and returns the progressive number associated to this request;
• handleRequest that gets the next request from the queue; if there are no requests left an exception should be thrown;
• giveUp that, given a progressive number eliminates the corresponding request from the queue; if there is no such request, an exception is thrown;
• waitingTime that, given a progressive number returns the number of requests that are queued before that request; if there is no such request, throw an exception;
• toString that returns a string representation of the request object, with one request per line.

Solution: representation of the objects, skeleton of the class, class Counter, class CounterException

Part 3. Implement a client class for Counter that contains a static method readFromFile that, given a string f that represents the name of a file containing names of persons, one per line, and a Counter c, adds for each person in the file a request to counter c, and returns an array containing the progressive numbers associated to the requests.

Solution

Part 4. Illustrate the mechnism of error handling in Java through exceptions.

Note: test the code you have developed by using the class defined in the file Main.java and the example file paperopoli.txt (containing the italian names of Disney comic book characters).