# Chapter 6: Intro to OOP

The exercises here are taken from my forthcoming book
The Java Developer's Resource.
## Quiz

- What's the difference between an object and a class?
- What's the difference between an instance of a class and an object in that class?
- What's the difference between a local variable and a member variable?
- What's the diffidence between a static field and a non-static field?

## Exercises

- Convert the command line programs of exercises 1, 5, 7, 8, 9, 10, 11, and 12 from chapter 4 into methods that do the calculations but don't handle any input. Then write a main method to handle the input and call the new methods. Do you notice anything similar about the new main methods?
- Java lacks a complex data type. Write a Complex class that represents a single complex number and includes methods for all the usual operations, i.e. addition, subtraction, multiplication, division, etc.
- Hard: Create a VeryLong class that will store an integer of arbitrary length. The methods of this class should be similar to those of the Complex class.
- Using the VeryLong class of the last problem, create a Rational class that handles arbitrarily precise fractions.
- Hard: Modify the toString() method of the Rational class so that it outputs results as mixed numbers in reduced form (i.e. 1 + 3/8 instead of 1 + 6/16 or 11/8). Hint: The greatest common denominator of two numbers u and v is the same as the greatest common denominator of u and u - v.

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Copyright 1996 Elliotte Rusty Harold

elharo@sunsite.unc.edu

Last Modified August 20, 1996