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Trail: Learning the Java Language
Lesson: Object Basics and Simple Data Objects

## Questions and Exercises: Creating and Using Objects

### Questions

> 1. What's wrong with the following program?

>    >     public class SomethingIsWrong {
>    >         public static void main(String[] args) {
>    >             Rectangle myRect;
>    >             myRect.width = 40;
>    >             myRect.height = 50;
>    >             System.out.println("myRect's area is " + myRect.area());
>    >         }
>    >     }

> 2. The following code creates one `Point` object and one `Rectangle` object. How many references to those objects exist after the code executes? Is either object eligible for garbage collection?

>    >     ...
>    >     Point point = new Point(2,4);
>    >     Rectangle rectangle = new Rectangle(point, 20, 20);
>    >     point = null;
>    >     ...

> 3. How does a program destroy an object that it creates?

### Exercises

> 1. Fix the program called `SomethingIsWrong` shown in Question 1.
> 2. Given the following class, called `NumberHolder`, write some code that creates an instance of the class, initializes its two member variables, and then displays the value of each member variable.

>    >     public class NumberHolder {
>    >         public int anInt;
>    >         public float aFloat;
>    >     }

Check your answers.

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