Transcript CS/IS 112 – Week 2 - Glendale Community College

CS/IS 112 – Week 2
• Logic Problem
• More Java background and
basics
• Values Variables, and
operations
Easy Logic Problem 1a
Solving computer programming assignments involves paying attention to details
And figuring out your own best tools for solving detailed problems
Claude has a facility for learning languages. In each of the last four years (2002 through 2005), he has set himself the
task of learning a different language so that, by the end of the year, he could vacation in a country where the language is
spoken and make himself understood. He learned each language through a different method (in one case, through
conversation with a native speaker). Discover the year in which Claude learned each language and the method he
utilized.
1.
2.
3.
4.
Claude learned Spanish (which he did not pick up by listening to audio tapes) during an odd-numbered year.
He learned Finnish in 2003
He learned Korean by watching vides.
Polish (which Claude did not learn in 2004) is not the language that he learned by reading books or listening to tapes.
YEAR
Language
Method
2002
2003
2004
2005
__________
__________
__________
__________
_________________________
_________________________
_________________________
_________________________
S
2002
2003
2004
2005
Books
Conv
Tapes
Videos
F
K
P
Bk
Con Tp
Vi
Classes and Objects
• CLASS – A single unit that defines both the data
that will be used and the operations that can be
performed on the data
• Operations in the above definition are formally
referred to as METHODS (informally they are
procedures and functions
• OBJECT is a specific item in a class
• Characteristics of an object are its ATTRIBUTES
The Traditional
Translation Process
Figure 1.8:
Figure 1.9:
Compiling and
Executing a
Java Program
A Well-Designed Program
Is Built Using Modules
Java identifiers
• Identifiers are just programmer defined names for things
and names are case sensitive at all times in Java
• Rules
– First character cannot be a digit
– Can contain letters, digits, underscore’_’ and dollar signs’$’
– Cannot be a Java keyword
• Shoulds – For this class MUSTs (conventions)
– We will use the book conventions
– Identifiers should be mnemonic
– All identifiers except for a class name should begin with a
lowercase character
– First letter of each following word in the identifier should be
capitalized
– First letter of class names should be capitalized
Java Programming Basics
• // Everything to the right of the double slash
is a human comment
• /* and */ Large block comment delimiters
• public class classname (classname must
match your sourcecode file name)
• { } braces mark the beginning and end of a
class
More Java basics
• public static void main (String[] args)
Every application (not applet) must have a
method name main. Every class must
contain at least 1 method
• { } Braces also mark the beginning and end
of each method
• System.out.print(“Hello World!”);
Methods contain statements and each
statement is terminated by a ‘;’
print and println methods
• System.out.print(“Hello World!”);
• General syntax
– objectname.print(data);
• General Java Class called System
– out is a specific object within that class
– Referred to as Standard Output Stream
– On most systems this is the video monitor
• The print method leaves the cursor right
after the last character
• The println method always moves the
cursor to the beginning of the next line
Hello World Basic Java
//File: DisplayHelloWorld.java
//Description: Displays Hello World!
//Programmer: Bruce Haft
//Date: 2/27/2006
public class DisplayHelloWorld
{
public static void main(String[] args)
{
System.out.print(“Hello World!”);
} // end of main() method
}
showMessageDialog()
Dialog Box:
QUESTION_MESSAGE
Figure 1.16b:
Hello World Dialog Box
//File: DisplayADialog.java
//Description: Construction of a dialog
//Programmer: Bruce Haft
//Date: 2/27/2006
import javax.swing.*;
public class DisplayADialog
{
public static void main(String[] args)
{
JOptionPane.showMessageDialog(null,"Hello World!",
"Sample",JOptionPane.WARNING_MESSAGE);
System.exit(0);
} // end of main() method
}
Data Types
•Primitive Data
•Operations on primitive data type are provided by
arithmetic symbols
•Reference Data
•Operations provided as methods
Figure 2.1:
Primitive Data Types
Integer data types
Type
byte
short
int(def)
Storage
1 byte
2 bytes
4 bytes
long
8 bytes
Range
-128 to 127
-32,768 to 32,767
-2,147,483,648 to
2,147,483,647
-9,223,372,036,854,775,808
to 9,223,372,036,865,775,807
Floating Point
Type
float
Storage
4 bytes
double(def)
8 bytes
Range of values
Precision of values
Exponential notation
Range of Values
1.40129846432481707e-45 to
3.40282346638528860e+38
4.94065645841246544e-324 to
1.79769313486231570e+308
Figure 2.2:
Reference Types
Characters
• Stored in 16-bit unsigned values Unicode
• Java provides a class named String for
manipulating this type of data.
• String type is a reference type
• Most operations for strings will be methods
rather that arithmetic symbols
The Letters JEANS
Stored by
a Java Program
Figure 2.3:
Escape Sequences
• The backslash (\) character causes Java to
interpret the character that follows
differently
–
–
–
–
–
–
–
–
\b
\f
\n
\r
\t
\\
\’
\”
move back one space
move to the next page
move to the next line
carriage return
move to the next tab setting
backslash character output
single quote output
double quote output
Boolean Constant
• A type of data that is restricted to one of
two values
– True
– False
• Cover more when we talk about decisions in
Chapter 4
An Example of a Value
Stored in a Reference Variable
Figure 2.8:
Figure 2.9a:
Creating a Reference
Variable
Instantiating an
Object
Figure 2.9b:
The Location of
Different Strings Using the Same
Reference Variable
Figure 2.10:
LoanCalculator.java
/* File: LoanCalculator.java
Sample loan calculation program written in
plain Java
by: Bruce Haft <<< for Extra credit submission
PUT YOUR NAME HERE
February 20, 2006 <<< change the date to the
last date you made a change
*/
import java.text.*; //needed for formatting
import java.io.*; //needed to access input stream
classes
public class LoanCalculator
{
More LoanCalculator.java
public static void main (String[] args)
throws java.io.IOException
{
String s1, s2, s3;
double interestRate, loanAmount, interest, payment,
numerator, denominator;
int numYears;
int paymentsPerYear = 12;
DecimalFormat num = new DecimalFormat(",###.00");
// needed for conversion
InputStreamReader isr = new
InputStreamReader(System.in);
// needed to use readLine()
BufferedReader br = new BufferedReader(isr);
More LoanCalculator.java
System.out.print("Enter loan amount: ");
s1 = br.readLine();
loanAmount = Double.parseDouble(s1);
System.out.print("Enter interest rate in decimal: ");
s2 = br.readLine();
interestRate = Double.parseDouble(s2);
System.out.print("Enter number of years for the loan: ");
s3 = br.readLine();
numYears = Integer.parseInt(s3);
Next Week
• Finish Chapter 2
• Start Chapter 3
• All Extra Credit due by 3/13
Last Loancalculator.java
numerator =( loanAmount * ( interestRate / paymentsPerYear));
denominator = 1 - Math.pow((1 + (interestRate /
paymentsPerYear)),
(-paymentsPerYear * numYears));
payment = numerator / denominator;
interest = ( paymentsPerYear * payment * numYears ) -loanAmount;
System.out.print("\n\nThe monthly payment on the loan would be "
+ num.format(payment));
System.out.print("\n\nThe total interest on a loan of $"
+ num.format(loanAmount) + " for " + numYears + " years\n");
System.out.print("at a rate of " + num.format(100 *
interestRate) + "% would be $" + num.format(interest));
}
}