1. Chapter 1: An Overview of Computers and Programming Languages
CSC 111 Java Programming I
Chapter 1: An Overview of Computers and Programming Languages

2. Chapter Objectives Learn about the evolution of programming languages
Examine high-level programming languages
Discover what a compiler is and what it does
Examine how a Java program is processed
Learn what an algorithm is and explore problem-solving techniques
Become aware of structured and object-oriented programming design methodologies
Java Programming: From Problem Analysis to Program Design, Third Edition

3. Evolution of Programming Languages
Computers have greatly affected our daily lives, helping us complete many tasks.
Computer program (software) is created with Programming languages which is easier for humans to read and write.
Programming languages (High-level languages) are a bridge between human languages and computer instructions (low level languages).
Basic, FORTRAN, COBOL, C/C++ and Java all are examples of programming languages
Java Programming: From Problem Analysis to Program Design, Third Edition

4. History Of Java
Developed by Sun Microsystems – a company known for its workstations .
Java is well known for developing internet applications. it is used to :
Create web pages with dynamic and interactive content.
Develop large –scale enterprise applications.
Enhance the functionality of WWW servers .
Provide applications for customer devices ( ex . Cell phones) .
Java programs can run from a web browser.
Java Programming: From Problem Analysis to Program Design, Third Edition

5. History Of Java
Java is portable. Your programs will run on your home computer and the Uni computers without changes.
Rich library. You can take advantage of code that is already written to do many commonly needed tasks and write more complex programs earlier.
Java Programming: From Problem Analysis to Program Design, Third Edition

6. So… What is programming?
What do you think programming is?
Programming is, basically, solving a problem using a computer.
More formally: Programming is the process of translating a problem we want solved into software that runs (successfully) on a computer.
Java Programming: From Problem Analysis to Program Design, Third Edition

7. So… How do we learn to program?
Practice, practice and more practice !!!
Like learning to swim …
You wont learn by reading the book!
You wont learn by copying from other students!
You wont learn by not doing it
You need to get confidence in
1. Using the environment
Your computer, editors, compilers, running programs
2. How to construct programs
• Understanding the features of the language
• This is what mostly what we cover in lectures
• Planning (i.e., thinking!)
3. Getting the program to work
• Compiling, testing, debugging
Need to get good at all three
Java Programming: From Problem Analysis to Program Design, Third Edition

8. Basics of Java Environment
The environment
The language
Java applications programming Interface API
Various class libraries
Java Programming: From Problem Analysis to Program Design, Third Edition

9. Processing a Java Program
A Java program undergoes several stages :
Editing: use Java code and save in a text file named
className .java ( source program ).
2. Compiling : the compiler checks the source program for any syntax errors then translates the program into code understood by interpreter called bytecode saved in a file named className.class
3. Loading : the .class file is loaded into computer main memory for execution, and connected to all classes.
4. Verifying : to validate and secure against damage .
5. Interpreting :the Interpreter reads and translates each bytecode instruction into machine language and then executes it , one instruction at a time .
Java Programming: From Problem Analysis to Program Design, Third Edition

10. Processing a Java Program
Java Programming: From Problem Analysis to Program Design, Third Edition

11. Processing a Java Program
Java Virtual Machine (JVM): A hypothetical computer developed to make Java programs machine independent ( i.e run on many different types of computer platforms ).
Bytecode is the machine language for the JVM .
Java Programming: From Problem Analysis to Program Design, Third Edition

12. Processing a Java Program
Two types of Java programs:
Applications : standalone programs stored and executed on a local computer .
Applets : small programs stored on remote computers that users connect to via a WWW browser. Applets are loaded into the browser , executed then discarded .
Java Programming: From Problem Analysis to Program Design, Third Edition

13. What does a Java program look like? Example 1
A simple Java application:
an application executes using the Java interpreter.
The basic unit of a Java program is a class.
Every Java program must have at least one class .
Each class begins with a class declaration that defines data and methods for the class . We’ll talk about this more later.
Java Programming: From Problem Analysis to Program Design, Third Edition

14. What does a Java program look like? Example 1
Here’s a class called Welcome:
public class Welcome {
// This is a comment. }
It’s a convention that the name of a class starts with a capital letter.
You’ll meet other conventions along the way!!
At the moment, we’ve defined a class that does nothing. The line with
the // in front of it is not translated by the compiler - it’s called a comment
and it’s ignored.
So let’s make our program do something!
Java Programming: From Problem Analysis to Program Design, Third Edition

15. What does a Java program look like? Example 1
public class Welcome {
public static void main(String [] args)
System.out.print(“Welcome to Java”); }
We’ve now added a main method to our class. We’ve also used a
number of words that have a special meaning to Java: class, public,
static, void and String.
The line System.out.print(“Welcome to Java ”) is an instruction to print the sentence Welcome to Java on the screen.
The double quotes (“) are not printed out as they are used to inform the compiler that Welcome to Java is a String.
Then our program exits.
Java Programming: From Problem Analysis to Program Design, Third Edition

16. What does a Java program look like? Example 1
public static void main (String args[]) is a part of every Java application program.
Java applications automatically begin executing at main()
The void before main() means that main will not return any info .
A Java class must contain one main method if it is an application .
Java Programming: From Problem Analysis to Program Design, Third Edition

17. What does a Java program look like? Let’s make it work !
1. Type the program into a text editor
2. Save as Welcome.java
3. Compile into byte codes
javac Welcome.java
4. Execute byte codes
java Welcome
Java Programming: From Problem Analysis to Program Design, Third Edition

18. What does a Java program look like? Let’s work it !
Java Programming: From Problem Analysis to Program Design, Third Edition

19. What does a Java program look like? Remember !
Upper case and lower case are very important! Java is case-sensitive. ( A is NOT similar to a)
Your class name MUST MATCH YOUR FILE NAME.
You only use the class name when you invoke Java but you use the file name when you invoke the compiler (Javac).
A file cannot contain two public classes.
Java Programming: From Problem Analysis to Program Design, Third Edition

20. What does a Java program look like? Example 2
public class ASimpleJavaProgram {
public static void main(String[] args)
System.out.println("My first Java program.");
System.out.println("The sum of 2 and 3 = " + 5);
System.out.println("7 + 8 = " + (7 + 8)); }
Class name
Java
o/p
stmts
Body of class
Heading of method main
Java Programming: From Problem Analysis to Program Design, Third Edition

21. What does a Java program look like? Example 2
A Java output statement causes the program to evaluate whatever is in the parentheses and display the result on screen .
+ is used to concatenate the strings . The system automatically converts the number 5 into a string ,joins that string with the first string ,and displays it .
Java Programming: From Problem Analysis to Program Design, Third Edition

22. What does a Java program look like? Example 2
The parentheses around 7+8 causes the system to add the numbers 7 and 8 ,resulting in 15 .
The number 15 is then converted to string 15 and joined with string “7+8”= “ .
Sample Run:
My first Java program.
The sum of 2 and 3 = 5
7 + 8 = 15
Java Programming: From Problem Analysis to Program Design, Third Edition

23. Internet ,WWW and Java
Internet : is an interconnection of networks that allows computers around the world to communicate with each other .
In 1970’s , the US DOD developed techniques to interlink networks , i.e communication protocols so that networked computers could communicate
Java Programming: From Problem Analysis to Program Design, Third Edition

24. Internet ,WWW and Java
WWW uses s/w programs that enable users to view documents on any computer over the internet
The primary language of web is HTML , a simple language for laying out and linking documents .
HTML is not capable of interacting with users except to collect info via simple forms .
Java applets make the web responsive and interactive
Java Programming: From Problem Analysis to Program Design, Third Edition

25. Java Applet Example Brush1.java Brush1.class Brush1.html
Java Programming: From Problem Analysis to Program Design, Third Edition

26. Problem-Analysis-Coding-Execution Cycle
Algorithm: a step-by-step, problem-solving process in which a solution is arrived at in a finite amount of time.
Pseudocode: an “outline” of a program that could be translated into actual code. It is a technique to show the programming steps.
Java Programming: From Problem Analysis to Program Design, Third Edition

27. Example Design an algorithm to find the perimeter and area
of a rectangle.
Steps:
Get the length of the rectangle.
Get the width of the rectangle.
Find the perimeter using: perimeter = 2 *(Length + Width)
Find the area using: area= Length * Width
Java Programming: From Problem Analysis to Program Design, Third Edition

28. Problem-Solving Process
Analyze the problem: Outline solution requirements and design an algorithm.
Implement the algorithm in a programming language (Java) and verify that the algorithm works.
Maintain the program: Use and modify if the problem domain changes.
Java Programming: From Problem Analysis to Program Design, Third Edition

29. Problem-Analysis-Coding-Execution Cycle
Java Programming: From Problem Analysis to Program Design, Third Edition

30. Programming Methodologies
Two basic approaches to programming design:
Structured design
Object-oriented design
Java Programming: From Problem Analysis to Program Design, Third Edition

31. Structured Design A problem is divided into smaller sub-problems.
Each sub-problem is analyzed, solved and a solution for this sub-problem is obtained.
The solutions of all sub-problems are combined to solve the overall problem.
Is called structured programming , top-down design approach, or modular programming .
Java Programming: From Problem Analysis to Program Design, Third Edition

32. Object-Oriented Design (OOD)
In OOD, a program is a collection of interacting objects.
An object consists of data and operations.
Steps in OOD:
Identify the objects which form the basis of the solution , then determine how these objects interact with each other .
Example : write a program that automates the video rental process for a video store .
The two main objects are : 1- video
2- customer
Java Programming: From Problem Analysis to Program Design, Third Edition

33. Object-Oriented Design (OOD)
Steps in OOD:
2. Specify the relevant data for each object and the possible operations to be performed on that data .
Example : for the video object
the data might be :
movie name ,Starring actors ,and Number of copies in stock.
The operations on video object might include :
checking the name of the movie , reducing the # of copies in stock by 1 after renting a copy .
Java Programming: From Problem Analysis to Program Design, Third Edition

34. Object-Oriented Design (OOD)
Each object consists of data and operations on those data
The final program is a collection of interacting objects.
More on that in CSC113.
Java Programming: From Problem Analysis to Program Design, Third Edition