Question

Create class RandomMyshapecontrollex that extends class My Shapecontroller and adds random Myshape subclasses with random sizes, colors and other properties to the DxawingMode1. In method startshape, class RandomMyshapeController should prompt the user for the number of random shapes to add to the drawing. Create a new My ShapeControllexFactory subclass (Fig. 5.18) named RandomMyshapeContro11erFactory that constructs a RandomMyshapeControllex when the string "Random" is passed to method newMyshapecontrollex. [Hint: Be sure to override method getSupportedshapes of class MyShape Contro11er \(F\) actory to return a String array that includes the String "Random".]

Short answer

Extend `MyShapecontroller` for random shapes and implement a factory class to instantiate it when 'Random' is specified.

Step-by-step solution

Understanding the Task

The task is to create a subclass `RandomMyshapecontrollex` that inherits from `MyShapecontroller`. This subclass will generate random shapes with various properties in the `DxawingMode1`. Additionally, a factory class `RandomMyshapeContro11erFactory` is needed to create instances of the `RandomMyshapecontrollex` when specified.

Creating RandomMyshapecontrollex Class

Define `RandomMyshapecontrollex` by extending `MyShapecontroller`. Implement a method `startShape` that prompts the user for the number of random shapes. Use this input to generate random shapes with varying sizes, colors, and other properties and add them to `DxawingMode1`.

Implementing Random Shape Generation

Within `startShape`, use random number generation to determine various properties, such as size and color, of the shapes. Use Java's `Random` class for generating these random values, ensuring you apply them when creating instances of `MyShape` subclasses.

Creating RandomMyshapeContro11erFactory Class

Define `RandomMyshapeContro11erFactory` by extending `MyShapeControllerFactory`. Override the method `newMyshapecontrollex` to return a new `RandomMyshapecontrollex` instance when the input string is "Random".

Overriding getSupportedShapes Method

In `RandomMyshapeContro11erFactory`, override the `getSupportedshapes` method. Return a `String[]` that includes "Random" among the supported shapes.

Key concepts

Class Inheritance

In Java programming, class inheritance is a fundamental concept that allows a child class to inherit properties and behaviors from a parent class. This concept supports the creation of more specific classes based on generic ones. It helps in reusing code and establishing a relationship between classes.

When you create a subclass, it automatically inherits all the fields and methods of the superclass, except for constructors and initialization blocks. Subclasses can also have additional fields and methods of their own or override the methods of the superclass to provide custom behavior.

In the context of the provided exercise, `RandomMyshapecontrollex` is created as a subclass of `MyShapecontroller`. This means that `RandomMyshapecontrollex` can use and potentially override methods from `MyShapecontroller`, while also having the ability to implement its own functionality, such as random shape generation.

To create a subclass in Java, you use the `extends` keyword:

• Define the child class using `public class ChildClass extends ParentClass`.
• Override methods using the `@Override` annotation to implement or customize inherited methods.
• Access the superclass methods and fields directly or through the `super` keyword if you're modifying a method.

Factory Design Pattern

The Factory Design Pattern is a creational pattern used to define an interface for creating an object but allows subclasses to alter the type of objects that will be created. This pattern provides a way to encapsulate object creation in a manageable way, improving code modularity and allowing for greater flexibility when adding new types or changing implementations.

In the provided exercise, `RandomMyshapeContro11erFactory` is a factory class created to instantiate objects of the `RandomMyshapecontrollex` class when required. Factories are particularly useful when the precise type of the object created depends on some context or input, as with the keyword "Random" in this case.

A few steps to creating a factory pattern in Java:

• Create a factory class with a method that handles object creation (e.g., `newMyshapecontrollex`).
• Define the method to determine what object to create based on input parameters or context.
• Use `return` statements to instantiate and provide the required object type back to the caller.
• Override any necessary methods to support object creation, such as `getSupportedshapes` in this case to include "Random".

Random Number Generation

Random number generation is crucial for scenarios where unpredictability and variety is needed, such as games, simulations, and in this case, creating random shapes with different properties. In Java, the `Random` class in the `java.util` package offers a straightforward approach to generating random numbers.

The `Random` class can generate numbers, booleans, and other primitives, which can then be used to determine properties like the color, size, and position of shapes in a drawing application. Random number generation in the `RandomMyshapecontrollex` class ensures that each shape has unique attributes.

Here's how you can use the `Random` class:

• Instantiate a `Random` object: `Random rand = new Random();`
• Generate random integers: `rand.nextInt(bound)` for an integer within a specified range.
• Create random doubles: `rand.nextDouble()` which returns a double greater than or equal to 0.0 and less than 1.0.
• Use `nextBoolean()` for a random boolean value.

By adjusting the bounds and types, you can quickly tailor the randomness to suit your specific application needs.

User Input Handling

User input handling in Java involves capturing and processing input from users to alter the behavior of programs. This can be typically done through command-line interfaces or graphical user interfaces. In our exercise, the `startShape` method prompts the user for input to decide how many random shapes need to be generated and added to the drawing.

Java provides several classes to facilitate user input handling, such as `Scanner` for console input and various event handling techniques for GUI input. For command-line interactions, `Scanner` is a simple and effective class that reads user input from standard input streams.

To handle user input using `Scanner`:

• Create a `Scanner` object linking it to the standard input: `Scanner scanner = new Scanner(System.in);`
• Use methods like `nextInt()`, `nextLine()`, or `next()` to read different types of input based on requirements.
• Always close the scanner using `scanner.close()`, especially when it's no longer needed, to free resources.

These steps are integral to ensuring that your Java program can dynamically respond to user inputs, offering flexible and interactive experiences.