ANIMATIONS IN JAVA

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There are several ways to create animations in the Java programming language. In the following, it will be shown how to create an animation using a timer, ie. object of class Timer from package javax.swing. The animation is explained through two examples.
The first is a free fall animation, while the second is actually a continuation of the circular motion application.
The beginning of the example is on the Graphics in Java page - example​

Timer

The previous examples show drawing shapes on a panel without any animation. In order to create an animation for a certain shape to move in the two-dimensional plane of the panel, it is necessary to import an object of class Timer, which is located in the javax.swing package. A Timer object produces an event that repeats at a given time interval. In response to this event, the actionListener method is called each time, similar to clicking a button, except that the event is repeated here.
If the position of a certain geometric shape, e.g. moved the circle by a certain value of dx in the x direction with each call to the actionPerformed method. for a given time interval and that circle drawn again we would get the illusion of the movement of that circle.
The timer must first be declared, usually as an attribute for the class:

​Then you need to create a timer:​The timer constructor requires two parameters: the time interval in milliseconds at which the timer event is repeated and the object that implements the ActionListener interface and which represents the timer event listener. One such object is similar to the listener at the button, and that was explained earlier.
In order for the timer to start, it is necessary to start it:​The timer can also be stopped if necessary:

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VIDEO LESSONS

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Movingbody down trough inclinedplane-animation using processing.
How to make an application for basic animation of a body sliding down an inclined plane, where the user can only observe and not influence the animation, the possibility has now been added that by moving the square at the top of the inclined plane, the height of the inclined plane can be increased or decreased, thereby also changing the angle of inclination .
Read more on web page:
Analysis of sliding of a body down an inclined plane example

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EXAMPLE: Free fall:​

​Task text:
Simulate the free fall of a circle-shaped body
Solution:An object that represents a body will be described by the class Body that inherits Ellipse2D.Double:Figure 1: Creating animations in Java using a timer. Body class.​The constructor with parameters gets 4 parameters that define the rectangle in which the ellipse is inscribed, ie. circle in our case.
The Environment class stores environmental data: free fall path distance x, initial position H0, body radius, and current body position along the y axis.Figure 2: Creating animations in Java using a timer. Class Environment.The object on which the animation is drawn belongs to the Animation class that inherits JPanel:Figure 3: Creating animations in Java using a timer. Animation panel.​In the drawing, two objects of the physical bodyclass PhysicalObject and soil of the class Rectangle2D.Double were created, and that is the class in the java.awt.geom package. Here the y coordinate of the rectangle depends on the height of the window obtained by the getHeight () method of the object of the current class this, and the width of the ground is identical to the width of the panel, where the current width value can be obtained by the getWidth () method.
The "paint ()" method is called to a certain number of milliseconds as a result of firing a timer event, which is created and run in the main class within the constructor:Figure 4: Creating an animation in Java using a timer. Animation window.The figure shows the part of the main class in which the main method is located, and that is the beginning of the application. An app class of the FreeFallFrame class was created in it, that is. the class in which the main method is located. when creating an object, the constructor is called and the commands in the constructor are still executed. The figure shows too the part where the main window and timer are created, while other objects were created after them.The object representing the animation panel, the body, and the object storing the environment data are declared as attributes for the class. The body logically belongs to the animation panel, so the reference of the body object is stored inside the animation panel as its attribute:The attributes of this class are:Figure 6: Creating animations in Java using a timer. FreeFallFrame class.​As attributes of this class, in addition to those already mentioned, there are also g-gravitational acceleration, dt-time interval referred to by the timer event and plotting scales.
The FreeFallFrame class implements the ActionListener interface, so an object of that class is also used to listen for timer events and button clicks. This object was passed to the timer constructor (see previous figures). In this example, the control panel is not created, only the possibility of its creation is left, which is left to the reader for practice.
The actionPerformed method looks like this:Figure 7: Creating animations in Java using a timer. Method actionPerformed.​First, the changed value of the velocity in the interval dt is calculated, and for the gravitational acceleration g. Since time is in s, and dt in milliseconds, it is necessary to divide dt by 1000.
Then the change of the y coordinate in that interval dt is calculated. It should be noted that the lower the dt, the more accurate the result. In order to move the body to a new position, the setFrame method is used, where x, y, w and x of the rectangle (in this case the square) in which the ellipse (circle in this case) is inscribed are passed as arguments.
By calling the repaint method, the paint method is called, which redraws all objects, including the body, but now in a new position.

EXAMPLE: Circular motion animation:​

Task:
Make a simulation of circular motion in a plane. Enable entering the radius of the circular path as well as the angular velocity. Based on the entered values ​​for r and W, calculate: V, ac and display the values ​​in the report field
Solution:This is an example of a circular motion shown in the previous chapter where a graph of the circular motion was made, as well as the entry of data on the angular velocity and the radius of the path by clicking on the input button. The timer should be introduced below and, as a reaction to the timer event, first calculate the change in line velocity and particle position when the time dt changes equal to the interval between the two timer events. The particle should be moved to a new position using the setFrame method, and then all objects should be drawn again. To change the velocity vector (shown by line only), you should use an object of the affineTransform class that has methods for rotating and translating a shape. When you start the application, the initial graphic is displayed: On the left is the drawn path, particle and velocity vector for the default values ​​of radius and angular velocity. On the right side is the input panel with fields for entering the radius r = 0.5m and the angular velocity W = 1, as well as the buttons for entering, for starting the animation and for stopping the animation. The code that performs this has already been shown and explained in the previous chapter.
If values ​​for r and W are entered in the input fields, for example r = 0.8m and W = 0.3s ^ -1 and the button for entering the values ​​of r, W and speed v is clicked, the drawing will be updated, as well as the drawing in accordance with the changed values: An increase in radius can now be seen, as well as an increase in the intensity of the velocity. This part is also explained in the previous chapter.
Clicking on any button, as well as when a timer event occurs, calls the ActionListener method: