1. String Output ICS 111: Introduction to Computer Science I
William Albritton
Information and Computer Sciences Department at the University of Hawai‘i at Mānoa
11/18/2018
© 2007 William Albritton

2. Problem Solving Computer science is basically about problem solving
So how do we solve a problem?
Take 3 main steps
Understand the problem
Make a plan
Implement the plan
11/18/2018
© 2007 William Albritton

3. Terminology
Like any other discipline, computer science has its own “fancy words” (jargon)
Computer scientists use the word algorithm for the plan that is used to solve a problem
Example algorithms from daily life
Taking the train from Makuhari to Nikko
Going scuba diving at 5 Caves, Maui
Teaching a friend to surf at Baby Queens
11/18/2018
© 2007 William Albritton

4. Writing Algorithms
When writing an algorithm, you need to follow a few rules
The algorithm must be a detailed series of steps that will solve the program
The algorithm can be written in many different ways
English (or Japanese, Chinese, Tagalog, etc.)
Drawings (diagrams, pictures, etc.)
Pseudocode (mix of English & a computer language)
The algorithm should be simple, unambiguous, and correct
11/18/2018
© 2007 William Albritton

5. Class Exercise 1 Critique the following algorithm
Algorithm to make spam musubi
Put rice in rice cooker
Cook the rice
Mash rice into ball
Put nori (seaweed) on top of rice ball
Cook spam on stove
Put spam on rice ball
11/18/2018
© 2007 William Albritton

6. Solving a Computer Problem
How can we get a computer to output a message to the screen?
So how do we solve a problem using the computer?
Take 3 main steps
Understand the problem
Make an algorithm
Implement the algorithm by editing, compiling, and running a computer program
11/18/2018
© 2007 William Albritton

7. 3 Steps for Computer Problem
Understand the problem
Make an algorithm
Output the message “Hello, World”
Implement the algorithm by editing, compiling, and running a computer program
See Program.java
11/18/2018
© 2007 William Albritton

8. Terminology Edit a program with an editor
Write program in Java language & store on computer
Creates Program.java (text file)
Compile a program with a compiler
Check for errors & create Java bytecode
Creates Program.class (bytecode file)
Run (execute) a program with an interpreter
Translate each bytecode to machine code & implement machine code
Creates screen output
11/18/2018
© 2007 William Albritton

9. Terminology Program Code Text file
A set of instructions for a computer
Also called “application”
Code
Contents of a computer program
Text file
A file of characters (text, or alphanumeric letters) that is used to store the computer program
Java programs end with *.java
For example, Program.java
11/18/2018
© 2007 William Albritton

10. Terminology Java language (Program.java) Java bytecode (Program.class)
Machine-independent, high-level computer language
Easy for humans to write & understand
Java bytecode (Program.class)
Machine-independent, low-level language
Java bytecode can be executed on any computer
Machine code (created by interpreter)
Machine-dependent, low-level language
For example, an IBM computer only understands IBM machine code
11/18/2018
© 2007 William Albritton

11. Software Installation
See the ICS 111 class webpage for instructions on how to install the software
JDK (Java Development Kit)
Used to compile programs
Also includes JRE (Java Runtime Environment) which is the interpreter used to run programs
jGRASP (Graphical Representations of Algorithms, Structures and Processes)
An IDE (Integrated Development Environment) used to edit, compile, and run programs
11/18/2018
© 2007 William Albritton

12. Java Language Syntax
Similar to human languages, Java also has syntax or grammar rules to follow
If we don’t follow these rules, the compiler will tell us
Syntax for a basic Java computer program
If you write your program in a different way, it may have syntax errors & not compile
public class ProgramName{
public static void main(String[] args){
//program code }
11/18/2018
© 2007 William Albritton

13. Program Name & File Name
Syntax for a basic Java computer program
public class ProgramName{
public static void main(String[] args){
//Write your program code here! }
Don’t worry about what all these words mean yet
We will learn later what public, class, [], static, void, args (arguments) mean
Just know that your program code goes inside the two inner curly brackets, i.e. "{" & "}"
Also, the file name must match the ProgramName
11/18/2018
© 2007 William Albritton

14. Terminology String A sequence of characters between double quotes
"Aloha!" is a string
is a string
"this is a string" is a string
In order to output a string to the computer screen, you need to use the following code, and put your string inside the parentheses
System.out.println("Hey, y'all!");
Also, don’t forget the semicolon at the end of every line of code
11/18/2018
© 2007 William Albritton

15. Class Exercise 2
Write a Java program that outputs a greeting in each language that each person of your group speaks
Question: What is the name of your file that you will use to store your program?
public class MyProgram{
public static void main(String[] args){
System.out.println("Hey, y'all!"); }
11/18/2018
© 2007 William Albritton

16. Meaning of class Meaning of each word on the first line of a program
public class ProgramName
public: this class can be used outside of its package (folder)
class: a class is the basic building block of the Java language & can be used as a blueprint to create objects
ProgramName: this is the name of your program & the name of your file
11/18/2018
© 2006 William Albritton

17. Meaning of main Meaning of each word of the main method
public static void main(String[] args)
public: other classes can use this method
static: this is a class method, so method call has format ClassName.methodName()
void: this method does not return anything
main: name of this special kind of method which is used to start the program
String[]: an array of Strings
args: the parameter of this method, which contains each word entered on the command line, stored as an array of Strings
11/18/2018
© 2006 William Albritton

18. A Messy Program This is how not to write a program!
See thisisonemessyprogram.java
Pressing the “Generate CSD” button in jGRASP will help to fix this
The “Control Structure Diagram” automatically indents your code
Also shows the structure of your code
11/18/2018
© 2007 William Albritton

19. Java Coding Standard
In ICS 111, we have a Java Coding Standard that should be followed when writing programs
The main purpose is to make sure the programs are neat and easy to understand
See the “links” column of the class webpage
Again, don’t freak out if you don’t understand what everything means yet
11/18/2018
© 2007 William Albritton

20. Terminology Comments Notes about the program for the reader
Ignored by the computer
Your program should read like a book!
Other people should be able to easily understand it
You should be able to easily understand it, so you can use it later to review for the exams
11/18/2018
© 2007 William Albritton

21. Types of Comments Single-line comments // Multi-line comments
Begin with /* and end with */
Javadoc comments
A way to comment your code, so that it can be automatically documented
See Java Coding Standard on webpage under “links”
Important as code increases in size & complexity
Easy for other folks to understand your code
Press the “Generate Documentation” icon (an open book) in jGRASP to see this
11/18/2018
© 2007 William Albritton