Object Design

Object Design
> Click or hit Control-Enter to run Example.main above

public class Example {
  // Both class and instance variables can be initialized
  public static int classNum = 8;
  public int objectNum = 4;

  // objectNum shadows this.objectNum... I'd pick a better name
  public void incrementObject(int objectNum) {
    this.objectNum += objectNum;
    classNum += objectNum;
  }
  // classNum shadows Example.classNum... I'd pick a better name
  public static void incrementClass(int classNum) {
    Example.classNum += classNum;
  }
}

Let’s review our scoping rules.

Work to the left.
Remember that method parameters can shadow (or conflict with) class or instance variables.

> Click or hit Control-Enter to run Example.main above

class Example {
  /** The number of hours of sleep you should get per night. */
  public static final int HOURS_PER_NIGHT = 8;
  ...
}

In Java a final variable cannot be modified.

You usually see this done to establish useful constant values—which can be either public or private

> Click or hit Control-Enter to run Example.main above

public class Example {
  public static void main(String[] unused) {
    System.out.println("How did I get here?");
  }
}

You’ve been using and even writing main methods? But what is it?

public class Example {
  public static void main(String[] unused) {
    System.out.println("And this is it!");
  }
}

When Java runs your program, execution has to start somewhere.
If a class has a main method Java can execute that class and begin the process of running a program.
So every Java application starts in main somewhere.

public class Example {
  public static void main(String[] unused) {
    System.out.println("And this is it!");
  }
}

But why is main passed an array of Stringss (that we usually ignore)?

We frequently use Java objects to model real objects or entities.

Objects allow us to design software that deals with things in realistic and natural ways.

> Click or hit Control-Enter to run Example.main above

> Click or hit Control-Enter to run Example.main above

MP3 is due Friday.
My office hours continue today at 11AM in the lounge outside of Siebel 0226. I’ll need to leave a bit early today.

Scope and Name Resolution

`final` and Constants

Let’s Talk `main`

Everything Has To Start Somewhere

But What About `unused`?

(Short Demo)

Object Modeling

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