Hydraulic System Simulation

Design and implement a program to manage the simulation of an hydraulic system.
All the classes must belong to the package hydraulic.

R1. Elements and pipes

A hydraulic system is composed of elements (of different types) connected to each other (through pipes that are not explicitly modeled in the system).

A system is represented by an object of class HSystem that allows adding new elements through the method addElement() that accepts as argument an object of class Element and adds it to the system components.

By means of method getElements() it is possible to get an array containing all and only the elements that compose the system.

R2. Simple elements

The simple elements are represented by the classes Source, Tap, and Sink.

All elements have a name that can be read through the getter method getName().
It is possible to connect the output of an element to the input of another element by means of the method connect() that accepts as argument the element whose input should be connected to the output of the subject: a.connect(b); connects the output of element a to the input of element b.

The invocation of method connect on a Sink object has no effect.

Given an element, it is possible to know to which other output element it is connected by means of the method getOutput() that returns an Element object.

R3. Complex elements

In addition to the simple elements described above, there are some complex elements. The "T" element, represented by class Split, allows splitting the input flow into two equal output flows. For this class, the connect() method accepts an additional argument specifying which output is being connected, such parameter may assume the values 0 for the first output and 1 for the second output.
For this class, it is possible to know which elements are connected to the outputs, by means of the method getOutputs() that returns an array with the two connected elements.

R4. Simulation

Given a valid system, i.e. a tree with a source as the root and where each path ends with a sink, it is possible to compute flow and how it is split among the distinct paths.

The computation takes place into two phases: in the first phase the parameters of the elements belonging to the system are defined, in the second phase the actual simulation starts.

During the first setup phase it is possible to:

define the flow of a Source through the method setFlow() that accepts a number representing the cubic meters per hour.
set the opening of Taps using the method setOpen() that accepts a boolean argument. When a tap is open the output flow is equal to the input flow, otherwise the output is zero.

For the T split the input flow is divided into two equal output flows (each a half of the input flow).

The simulate() method of class HSystem, performs the flow computations for each element in the system starting from each source (for the source, only the output flow, and for the sink just the input flow). This method requires as argument an object implementing the SimulationObserver interface, that provides a single method.

When, during simulation, the input and output flows are known for an element method notifyFlow() must be called on the observer passing the element type, the name, and the input and output flows; if any of the flows is not defined (e.g. for the Source and Sink), the constant NO_FLOW can be used.

Hint: given an object, to find out if it is an instance of a specific class the operator instanceof can be used.
E.g. if( element instanceof Source ).
Warning: you are not required to implement the interface SimulationObserver, you only need to use it; an example of implementation that simply prints to the console the notifications, is given in class PrintingObserver.