Graphics in java. Example circular motion

Figure 1: Creating graphical applications in Java. Example: Circular motion GUI.

Figure 3: Circular motion of the GUI. Constructor.Method createGUI:Figure 4: Circular motion of the GUI. Method createGUI.​First, a main window is created and the title, size and default behavior of the window are set when the X (close) button is clicked. Then a container panel was created and configured to schedule FlowLayout type components. This method of scheduling is by default, but an object of this class was created here because its constructor indicated that it wanted a cetral layout of the components, which would be 2 pixels horizontally and vertically within the panel. FlowLayout layout involves arranging the components in one row. as long as the components, according to their size, can be placed in that order, and then move to the next. The components will also be centered at a distance of 2 pixels.​Then, the left panel (Drawing class) and the right panel, the JPanel class are created. They are set to the Background color and preferred size. It should be noted that the left panel is not a JPanel class but a Drawing class that must inherit a JPanel class. This is because the panel could draw its own graphics by reworking the inherited paint method in the same way as in the previous example.
When the panel attributes are set, they are added to the container panel, which itself connects to the window with the setContentPane method.
Since the main class inherited the JFrame, it means that the object of that class is actually the window itself. The official word this was used to get the object of the class in which the given code is located.
Below the constructor, objects are created that represent the components needed to enter the data, set their attributes, and add them to the panel (add method):Figure 5: Circular motion of the GUI. Method createGUI-complete.The setVisible (true) method shows a window, i.e. sets visibility to true.
In the Drawing class, all variables and objects that represent the elements being drawn are first defined. Simple data is defined and some of it is initialized to some initial values ​​in the class, as class attributes. Objects are also declared out of methods but are created (defined) in the constructor. These are the center, the trajectory (circular line) and the particle moving along the trajectory (circle) of radius r (initial values ​​0.5 m). Since the dimensions of the drawing are in pixels where the width of the drawing is 500 pixels, the circle size of 0.5 is very small, so a scale (200 pixels per 1m) was introduced for drawing.
All three drawing objects are circles ie. ellipse whose rectangle is equal in width and height (square):Figure 6: Circular motion of the GUI. Class Drawing.In addition to creating these three objects, inside the constructor, you also calculate the line speed of the particle as well as the centripetal acceleration.
To remind, the Ellipse2D.Doubleclass is a class from the API (java.awt.geom package) that implements the Shape interface, so it can be passed to the Graphics2D class's draw and fill g2 object within the paint method:Figure 7: Circular motion of the GUI. Class Drawing. Paint method.​The color of the line (point making a circular motion) is set to red and its thickness to 3 (setStroke method (new BasicStroke (3));).
Only the initial circular motion position for the default parameter values ​​is drawn here, while the following will explain how to enter parameters by clicking on the button in the right panel and drawing a new drawing based on the entered values ​​and how to make a circular motion simulation by introducing a timer event.

A button click event in the circular motion example

In order to introduce a button click event, a class object that implements the ActionListener interface is required because that interface contains a method called in response to a button click. It is abstract in the interface and is completed in the class we associate with the interface with the official word implements. In the circular motion example, this is the main class: