When first learning programming concepts in my Introduction to Programming course, I came across data structures known as ArrayLists and classes. Previously, everything was done using arrays, so these were quite new and exciting. This is my first experiment using them, and one of the first mini-projects that really got me excited about learning more about algorithms and data structures.
The actual project (shown below) displays and recalculates the position of individual bouncing circles by iterating through every object on the screen every frame. As you can imagine, it would get laggy quickly! Click anywhere in the screen to release the bubbles.