teaswirll / gravity

gravity

You work for an educational software company that is developing a suite of simple Physics simulations. The code in gravity github repository is the beginning of a suite intended to permit the creation of a series of different types of pendulum simulation. You previously identified the AbstractEarthPendulum class as trivial and unnecessary, but figured it was mostly harmless. Now your team wants to be able to dynamically set which planet a pendulum is on during an interactive simulation, and to allow different kinds of gravity models that are impossible to represent with a single constant (e.g., latitude models).

Fork the gravity repository (https://github.com/ashrafcourses/gravity) to your own github account.

1. Run the main routine to see the expected behavior of the code.

2. Apply the refactoring approach "Collapse Hierarchy" to reduce the hierarchy levels by one. Ensure that the main routine still works as expected. Push your refactored code to the remote branch "RefactoringStep1".

3. Use the Strategy pattern to replace the field g with a reference to a strategy object. This should allow different kinds of gravity models to be associated with a Pendulum instance dynamically. Name the strategy interface GravityModel.

public interface GravityModel {
      public double getGravitationalField();
}

Objects implementing GravityModel will be initialized with all state required to produce the gravitational field value under their specific model, this occurs before being assigned to a pendulum. The pendulums will just use the model assigned to it via the GravityModel interface. Adjust the pendulum constructors so that a GravityModel is assigned on initialization, and add a new method that will allow the GravityModel to be changed dynamically. Define one concrete strategy called GravityConstant. This class simply receives a constant value for g in its constructor.

4. Run the main routine to ensure that the functionality hasn’t changed. Push your refactored code to the remote branch "RefactoringStep2".

5. Modify the provided main routine as follows:

• it initializes a SimplePendulum and a RegularPendulum with a GravityConstant object.
• let the pendulums swing for a little while, then assign a different GravityConstant object. For example, your first GravityConstant could represent the Earth’s gravitational field (9.81 m/s²), and the second could represent Jupiter’s (25 m/s²). Push your code to the remote branch "RefactoringStep3".