1. Introduction to Programming with Java
AP Computer Science
ASFA

2. What is an Object? A person, place, or thing
That knows something about itself
Has data (attributes, fields)
A cashier has a id, name, and a password
And can do something
Has operations (methods)
A cashier can total the items, take payment, make change
Point out objects in the room (like a book, pen, computer, person, etc). Talk about what type of object it is, what data it has, what it can do.
Go through your example real-world scenarios. Point out the objects, their types, data, and operations.
The picture is a cashier in a music store. The data is his name and password. The operations are how to “ring up” and “take payment”, and “make change”.
Intro-OO

3. What is a Class? The type of an object
The way we classify an object
“The Idiot” by Dostoevsky is a book
“War and Peace” by Tolstoy is a book
Caitlin is a cashier
Kheri is a cashier
Grouping of objects with the same data and operations
Objects are instances of a class. This slides shows two book objects of the class book.
Intro-OO

4. We will use the Java language to model our objects on the computer
Cashier has attributes:
Name
Id number
Cashier can perform:
Make change
Calculate order total

5. And instructions on how to perform:
This would be modeled in Java as a Cashier class with memory set aside to store:
Name
Id number
And instructions on how to perform:
Make change
Calculate order total
Aiden and Jordan are both Cashier objects
Aiden has a different name and id number than Jordan, but they both make change the same way

6. Now Let’s Look at the Small Steps
How are we going to make this happen through a computer program?

7. What is a computer? What is this programming thang? What is Java?
Part 1
What is a computer? What is this programming thang? What is Java?

8. What is a Computer?
A device that performs high-speed mathematical and/or logical operations or that assembles, stores, correlates, or otherwise processes information.
The first computers were people
who did computations
The picture shows the Harvard Computers which were women who did astronomical computations at Harvard University. See
See
See and for some of the history of computers
See for a history of computers.
See for some computers you may not be familiar with. Also see

9. Why Do Computers Keep Getting Cheaper?
The number of transistors (a major component of the brain of a computer) at the same price doubles every 18 months
making computers faster, smaller, and cheaper over time
This notion is know as Moore’s Law
For Gordon Moore, a founder of Intel
This “Law” has held true for decades
And is predicted to hold true at least one more
See for more information on transistors.
See for more information on Moore’s Law.
See for a picture of the first transistor.
See for a history of transistors.

10. What are Computers Good At?
Doing calculations and comparisons
Producing the same answer every time
Like calculating the sum of hundreds of numbers
Storing information
They don’t forget information
Looking up information quickly
Search through a phone book to find the customer name for a phone number
Notice that these are things that people aren’t great at.

11. What is Programming?
Creating detailed instructions that a computer can execute to accomplish some task.
Like writing a recipe for your favorite dish
Or giving someone directions to your house
Or making a robot do what you want
Put your favorite recipe on the coweb ( See if someone else can follow the directions.
Write down the directions to your house. See if someone else can follow them to find it.
Use LEGO Mindstorms RIS to build a robot and use Robocode to program it.

12. Early Programming
Early computers required the programmer to set switches and move wires
Which represented a series of 1’s and 0’s
Later computers were programmed using punched cards
The punch cards had first been used to program looms for weaving see
For a short history of programming see

13. Language Evolution
Early languages were based on how to do instructions on each machine
1’s and 0’s to add, subtract, read, store, etc
Assembler allowed you to write programs using names for instructions and memory
But still translated into machine language
Higher-level languages
Are compiled into machine language or virtual machine language (Java)

14. Java Developed at Sun in the early 1990s
Invented by James Gosling
Similar to C++ in syntax but easier to use
Less likely to crash
Automatic memory management
Cross-platform, object-oriented language
One of the fastest adopted technologies of all time
Current favorite language, for now
For more information on Java see
See for a sample program.
See for Sun’s Java web site. It has documentation and tutorials.
See for more on James Gosling.

15. Which Language?
All high-level languages are eventually translated into machine language
You can write the same program in any language
The computer doesn’t care what high-level language you use
The language matters to the programmer
How long does it take to write the program?
How hard is it to change the program?
How long does it take to execute?

16. Why Don’t We Just Use English?
English is good for communication between two intelligent humans
Even then we sometimes don’t understand
Computers are very stupid
They basically know how to add, compare, store, and load
Programs are very detailed instructions
Everything must be precise and unambiguous

17. Programming Exercise
Write down instructions for how to make a paper airplane
Have your partner read the directions and make an airplane
stop anytime anything isn’t clear and ask for clarification
Try doing other direction exercises. Write down directions for how to get to a classroom in the school. Write down directions for how to use a computer program.

18. Summary – Part 1 Computers perform calculations and comparisons
A program is a series of instructions to a computer
Programming has changed from moving wires to writing textual programs that can be stored and executed several times
Java is a high level popular programming language

19. How does the computer do it?
Part 2
How does the computer do it?

20. Parts of a Computer User Interface Brain - Central Processing Unit
monitor (screen), mouse, keyboard, printer
Brain - Central Processing Unit
can do math and logic operations
Memory - Storage
main - RAM
secondary – Disks, CD-ROMs, DVDs
See and
See
See for information on the hardware of a computer.

21. CPU – Brain of the Computer
Arithmetic/Logic Unit (ALU)
Does math and logic calculations on numbers in registers
Control Unit
Reads instructions from memory and decodes and executes them using the ALU
345
Add register A
to register B
263
608
Store the value
in register C into
memory location
All processing in a computer program happens in the CPU.
See for a nice overview of microprocessors (CPUs).
Numbers must be loaded into registers (high-speed storage areas) before they can be processed by the ALU.

22. Fetch, Decode, Execute Cycle
The control unit reads (fetches) an instruction from memory
The control unit decodes the instruction and sets up the hardware to do the instruction
like add the values in the A and B registers and put the result in the C register
The instruction is executed
The program counter is incremented to read the next instruction
The program counter can also be changed to “Jump” to another instruction which means that the value in the program counter is changed
See for information on how microprocessors work.

23. Processor Speed Processors (CPUs) have a clock
Clock speed is measured in megahertz (MHz) or gigahertz (GHz)
Some instructions take just 2-3 clock cycles, some take more
When the clock speed increases the computer can execute instructions faster
See for a comparison of processor speeds for several common processors.
One megahertz represents one million cycles per second. One gigahertz represents 1 billion cycles per second.

24. Memory Computer memory is used to store data
The smallest unit of memory is a bit (Binary digIT)
A bit can be off (no voltage) or on (has voltage) which we interpret to be 0 or 1
Memory is organized into 8 bit contiguous groups called bytes. A megabyte is 1 million bytes. A gigabyte is 1 billion bytes.
See

25. Types of Memory Registers Cache
Very high speed temporary storage areas for use in the CPU
Used for calculations and comparisons
Cache
High speed temporary storage for use with the CPU
Main Memory – Random-access Memory (RAM)
High speed temporary storage
Contains programs and data currently being used
Often described in Megabytes (MB)
Secondary Memory - Disks
Contains programs and data not currently being used
Often described in Gigabytes (GB)
Temporary storage loses the values stored in it after the power is turned off.
A megabyte is more than a million bytes. A gigabyte is more than a billion bytes.
See for more information on how memory works.

26. Why are there so many types of memory?
The faster memory is the more it costs
So we reduce the cost by using small amounts of expensive memory (registers, cache, and RAM) and large amounts of cheaper memory (disks)
Why do we need cache?
Processors are very fast and need quick access to lots of data
Cache provides quick access to data from RAM

27. How does Memory Represent Values?
The different patterns of the on and off bits in a byte determine the value stored
Numbers are stored using binary numbers
101 is 1 * * * 22 = = 5
1010 is 0 * * * * 23 = = 10
Characters are internally represented as numbers
Different numbers represent different characters
There are several systems for assigning numbers to characters:
ASCII, EBCDIC, and Unicode
See for information about ASCII. Most computers store text in ASCII. ASCII uses 7 or 8 bits to store characters.
See for information on EBCDIC. EBCDIC is used on IBM computers.
See for information on Unicode which is a 16 bit format that can represent Greek, Chinese and Japanese as well as English characters.

28. Binary Exercise
Count as high as you can using just the fingers on one hand
You have to count up by ones
No counting by 10s
The fingers can be up or down
No in-between states
How high can you count?
Show the students how to do this using binary numbers. Each finger represents a power of two.

29. Binary Numbers
We usually work with decimal numbers with digits from 0 to 9 and powers of 10
7313 = (7 * * * * 1)
Or (7 * * * * 100)
The binary number system uses digits 0 and 1 and powers of 2
0101 = (0 * * * * 1)
Or (0 * * * *20)
= 5
See for more information on number systems and binary numbers.

30. Binary Addition
To add two decimal numbers you add the digits and if the total is greater than ten you carry the one into the next column
To add two binary numbers
0 + 0 = 0
and = 1
1 + 1 = 0 with a carry of 1 into the next column to the left

31. It’s Hard to Work in Binary
Convert to Octal
Base 8
For example:
A is 65 in decimal and in octal
What is q in octal?
0161
Or Hexidecimal
Base 16
For example:
A is 65 in decimal and 0x41 in hexidecimal
What is a space in hex?
0x20

32. Decimal Number Storage
How do you think a computer stores: ?
It uses an IEEE 754 format
Converts the number into a value between 0 and 1 raised to a power of 2
Stores 3 things
A bit for the sign
A number between 0 and 1 (the mantissa)
The power of 2 (the exponent)

33. Encode and Decode Exercise
Use Unicode to write a secret message in decimal and then exchange it with another person
See Appendix B in the Java Concepts textbook for the decimal values for characters

34. Encodings Make Computer Powerful
Voltages are interpreted as numbers
Numbers can be interpreted as characters
Characters can be interpreted to be part of a link to Sun’s Java Site (formerly)
<a href= Java Site </a>
A byte of memory might contain the values “off on off off off off off on” which we assign the binary numbers of “ ” which is the encoding for the letter “a” in ASCII which could be part of a link to Sun’s Java web site.
Each layer of encoding is handled by software. a
off on off off off off off on

35. Summary – Part 2
Computers are commonplace and very important to modern life
Computers are made up of parts
CPU – calculation and comparisons
Memory – temp storage
Disk – permanent storage
Monitor – Display
Keyboard and mouse – User input
All data in a computer is stored in bits
More data takes more bits
All characters can be represented as a series of 0s and 1s

36. Introduction to Java, and jGRASP part 3

37. Introduction to Java, and jGRASP
Part 3
Introduction to Java, and jGRASP

38. What is jGRASP?
jGRASP is a free integrated development environment for doing Java programming
From Auburn University
The pane that shows the code (on the right) is called the definitions pane.
The pane that allows you to type Java expressions and see the result is called the interactions pane.

39. jGRASP We will use jGRASP to create our Java programs
But, first, we will use it to try out some mathematical operations

40. Math Operators in Java (+ * / - %)
Addition
3 + 4
Multiplication
3 * 4
Division
3 / 4
Subtraction
3 – 4
Negation -4
Modulo (Remainder)
10 % 2 and 11 % 2
The compiler interprets 3.0 as a double (floating point number) and 3 and 4 as integers. The result of an operation is in the same type as the values being operated on so the result of 3 / 4 is 0 since and integer can’t represent 0.75.
See for arithmetic operators in the Java tutorial

41. Math Operators Exercise
Open jGRASP and do the following in the interactions pane
Subtract 7 from 9
Add 7 to 3
Divide 3 by 2
Divide 4.6 by 2
Multiply 5 by 10
Find remainder when you divide 10 by 3
To open jGRASP double click on the jGRASP icon. You will see a small window which will show while it loads. It can take a few minutes to load.

42. Why is the result of 3 / 2 = 1? Java is a strongly typed language
Each value has a type associated with it
Tells the computer how to interpret the number
It is an integer, floating point, letter, etc
The compiler determines the type if it isn’t specified (literals)
3 is an integer
3.0 is a floating point number (has a fractional part)
The result of an operation is in the same type as the operands
3 and 2 are integers so the answer is an integer 1

43. Casting
There are other ways to solve the problem of 3 / 2 has a result of 1
You can make one of the values floating point by adding .0
3.0 / 2
3 / 2.0
The result type will then be floating point
Or you can cast one of the values to the primitive types: float or double
(double) 3 / 2
3 / (float) 2
Floating point means that the number is stored in two parts. The digits are stored (without the period) and the location of the period is stored as a power of 10.

44. Casting Exercise
Use casting to get the values right for splitting up a bill for 3 people of 19 dollars.
Try it first by hand
Try it in jGRASP without casting
Try it in jGRASP with casting

45. Java Primitive Types
Integers (numbers without fractional parts) are represented by
The types: int or short or long
235, -2, , etc
Floating point numbers (numbers with fractional parts) are represented by
The types: double or float
, etc
A single character is represented by
The type: char
‘a’ ‘b’ ‘A’ etc
True and false values are represented by
The type: boolean
true or false
The primitive types in Java are not objects. Java left some simple data types as primitives to speed computation.

46. Why so Many Different Types?
They take up different amounts of space
They have different precisions
Usually use int, double, and boolean
byte uses 8 bits (1 byte) 2’s compliment
short uses 16 bits (2 bytes) 2’s compliment
int uses 32 bits (4 bytes) 2’s compliment
long uses 64 bits (8 bytes) 2’s compliment
float uses 32 bits (4 bytes) IEEE 754
double uses 64 bits (8 bytes) IEEE 754
char uses 16 bits (2 bytes) Unicode format
A floating-point type (float or double) stores both the digits and the exponent.
See for more information on floating-point numbers.

47. Sizes of Primitive Types
8 bits
byte
8 bits
8 bits
short
int
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
long
float
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
double
8 bits
8 bits
char

48. Types Exercise Which type(s) take up the most space?
Which type(s) take up the least space?
What type would you use for
The number of people in your family
A grade
The price of an item
The answer to do you have insurance
The number of people in the class
The number of people in your school
The number of people in your state

49. Floating Point Numbers
Numbers with a fractional part
Stored as binary numbers in scientific notation is x 101
The sign (1 bit)
The digits in the number (mantissa)
The exponent (8 bits)
Two types
float – 6-7 significant digits accuracy
double – significant digits accuracy
The mantissa is stored in positive binary. The exponent is stored as positive binary but with the addition of the stored value to -126 for float and for a double. So an exponent value of 0 for a float is actually an exponent of -126.
See for more information.

50. Comparison (Relational) Operators
Greater than >
4 > 3 is true
3 > 3 is false
3 > 4 is false
Less than <
2 < 3 is true
3 < 2 is false
Equal ==
3 == 3 is true
3 == 4 is false
Not equal !=
3 != 4 is true
3 != 3 is false
Greater than or equal >=
3 >= 4 is true
3 >= 3 is true
2 >= 4 is false
Less than or equal <=
2 <= 3 is true
2 <= 2 is true
4 <= 2 is false
The symbol ‘=‘ does not test for equal in Java. It is used as an assignment statement.
See for the Java tutorial section on relational operators.

51. Comparison Operators Exercise
In jGRASP
Try out the comparison operators in the interactions pane
with numbers
3 < 4
4 <= 4
5 < 4
6 == 6.0
with characters (single alphabet letter)
Put single quote around a character
‘a’ < ‘b’
‘b’ < ‘a’
‘a’ == ‘a’
Characters are represented as numbers with letters that we think of as coming first in alphabetizing schemes having lower numbers than the later letters.

52. Operator Order The default evaluation order is
Negation -
Multiplication *
Division /
Modulo (remainder) %
Addition +
Subtraction -
The default order can be changed
By using parenthesis
(3 + 4) * 2 versus * 2

53. Math Operator Order Exercise – Dr. Java
Try * 4 + 5
Add parentheses to make it clear what is happening first
How do you change it so that happens first?
How do you change it so that it multiplies the result of and the result of 4 + 5?
In jGRASP expressions entered into the interactions pane are evaluated and the result is displayed on the next line.
For more information on jGRASP see

54. Summary – Part 3 Computers
Can do math
Can execute billions of instructions per second
Keep getting faster, smaller, and cheaper
Java has typical math and relational operators
Java is a strongly typed language
This can lead to odd results
integer division gives a integer result
You can use casting to solve this
Java has primitive types to represent integer and floating point numbers
Math operations have a default order
You can specify the order with parentheses

55. Hello World!! Our first Java program
public class FirstProgram {
public static void main( String[] args)
System.out.println(“ Hello World !!”); }