Question

{ Random Colors })$ Modify Exercise 12.28 to draw each of the 20 randomly sized shapes in a randomly selected color. Use all 13 predefined Color objects in an array of Colors.

Short answer

Create an array of 13 colors; randomly assign one to each of 20 shapes.

Step-by-step solution

Understand the Problem

We need to modify an existing exercise to draw 20 randomly sized shapes and assign each shape a random color selected from a predefined set of 13 colors.

Define the Colors Array

Create an array containing the 13 predefined Color objects. This array will be used to randomly select a color for each shape.

Loop to Generate and Draw Shapes

Write a loop that iterates 20 times, corresponding to the 20 shapes that need to be drawn. Within each iteration of the loop, you'll perform a series of tasks to generate a shape and then draw it.

Randomly Determine Shape Size

Inside the loop, use a random number generator to determine the size of each shape. The function or method you use will depend on your programming environment. For example, Java could use `java.util.Random` to generate random numbers.

Select a Random Color

Still inside the loop, generate a random index to select a color from the colors array. Make sure the index is valid (from 0 to 12) using a random number generator.

Draw the Shape

Using the randomly determined size and color, draw the shape. In this step, ensure you set the drawing color to the randomly selected color before rendering the shape on the canvas.

Key concepts

Random Number Generation

In Java programming, random number generation is vital for creating programs that require unpredictability, like games or simulations. Random numbers allow developers to add elements of surprise and variability. Java offers the `java.util.Random` class to facilitate this process with ease.
To generate a random number:

• Create an instance of the `Random` class, e.g., `Random randomGenerator = new Random();`.
• Use methods like `nextInt(n)` to generate an integer between 0 (inclusive) and the specified `n` (exclusive).

In our exercise, we use random number generation to determine both the size of a shape and its color index from a predefined list. By doing so, each shape comes out unique, contributing to a more dynamic visual outcome.

Graphics Programming

Graphics programming is a skill that empowers developers to create visual content within applications. In Java, this typically involves using the `Graphics` class and is often paired with setting up a drawing environment where you can render shapes, images, or text.
To draw shapes on a canvas:

• Define a method that takes `Graphics` as a parameter. This object is your interface to the drawing surface.
• Utilize graphics methods like `drawRect`, `fillOval`, etc., to draw various shapes.
• Colors and strokes can be set using `setColor` and `setStroke` methods, respectively, which influence how everything drawn will appear.

The key point in our exercise is to ensure the graphic context's color is updated based on the randomly selected color before drawing each shape. This way, every shape gets an individualized appearance.

Color Objects

In Java's AWT, `Color` objects represent colors within your graphics programming. Java defines a set of standard colors, such as Color.RED or Color.GREEN. Our exercise uses an array of 13 predefined `Color` objects to randomly assign colors to shapes.
To work with color objects:

• Initialize a `Color` object using predefined constants or by specifying RGB values.
• For custom colors, use `new Color(r, g, b, a)` where `r`, `g`, `b`, and `a` stand for red, green, blue, and alpha (transparency).
• Colors are set in the graphics context using the `setColor` method.

By incorporating random color assignments from this array, each shape on the canvas becomes visually distinct, creating a stimulating canvas.

Loop Constructs

Loops in Java allow you to repeat a block of code multiple times, and are essential for tasks like drawing multiple shapes. The `for` loop, `while` loop, and `do-while` loop are primary constructs available in Java. For this exercise, a `for` loop effectively controls the drawing process of 20 shapes.
Here's how you apply loops in shape drawing:

• A `for` loop is structured: `for(int i = 0; i < numOfShapes; i++)`, which iterates a fixed number of times.
• Within each iteration, you perform tasks like setting size, selecting color, and rendering the shape.
• Loops ensure repetitive and procedural tasks are efficiently managed with minimal code repetition.

This systematic approach using loops makes the task straightforward and efficient, handling complexities one iteration at a time.