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.

Exercise 11A

Implement 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).

The class should implement the following features:

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

Solution: Request.java

Exercise 11B

Implement a class Counter that stores a queue of all requests issued at the counter.

The class should implement the following features:

• a constructor to create an empty counter, that is a counter with an empty queue;
• a method 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;
• a method handleRequest that gets the next request from the queue; if there are no requests left an exception should be thrown;
• a method giveUp that, given a progressive number eliminates the corresponding request from the queue; if there is no such request, an exception is thrown;
• a method waitingTime that, given a progressive number computes the number of requests that are queued before that request; if there is no such request, throw an exception;
• a method toString that returns a string representation of the request object.

• The array's size is initially set to 10.
• If the array is full and addRequest is called to append one more request, create a new array double the size of the old one and copy the old array's content into the new one;
• If the array is less than one third full after calling handleRequest, create a new array half the size of the old one and copy the old array's content into the new one;

Solution: Counter.java, CounterException.java

Exercise 11C

1. create an initially empty Counter;
2. have the user input the name of a text file containing person's names (one name for each line); for each person add a request to the counter's queue;
3. ask the user repeatedly which of the following actions should be taken and perform them:
   • handle the next request from the queue;
   • give up a request (progressive number read from user input);
   • add a new request (person's name read from user input);
   • print the number of requestis left (waiting time) before the given request (progressive number read from user input);
   • quit the program;
   after each operation print out the queue.

Here is an example input file (it contains the italian names of Disney comic book characters): paperopoli.txt

Note: to open a file specify its absolute path (for example C:\java-projects\lab-11\paperopoli.txt) since BlueJ does not set the current directory path.

Solution: Client.java