CS/IS 112

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CS/IS 112 Week 2

• Logic Problem
• More Java background and basics
• Values Variables, and operations

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• 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.    Claude learned Spanish (which he did not
  pick up by listening to audio tapes) during an
  odd-numbered year.
• 2.    He learned Finnish in 2003
• 3.    He learned Korean by watching vides.
• 4.    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 __________ _________________________
•  

•  

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S F K P Bk Con Tp Vi
2002 2003 2004 2005 Books Conv Tapes Videos
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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

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Figure 1.8 The Traditional Translation Process
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Figure 1.9Compiling and Executing a Java Program
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A Well-Designed ProgramIs Built Using Modules
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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

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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

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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

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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

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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(He
llo World!) // end of main() method
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Figure 1.16b showMessageDialog() Dialog
BoxQUESTION_MESSAGE
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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

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Data Types

• Primitive Data
• Operations on primitive data type are provided by
  arithmetic symbols
• Reference Data
• Operations provided as methods

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Figure 2.1 Primitive Data Types
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Integer data types

• Type Storage Range
• byte 1 byte -128 to 127
• short 2 bytes -32,768 to 32,767
• int (def) 4 bytes -2,147,483,648 to
• 2,147,483,647
• long 8 bytes -9,223,372,036,854,775,808
• to 9,223,372,036,865,775,807

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Floating Point

• Type Storage Range of Values
• float 4 bytes 1.40129846432481707e-45 to
• 3.40282346638528860e38
• double(def) 8 bytes 4.94065645841246544e-324 to
• 1.79769313486231570e308
• Range of values
• Precision of values
• Exponential notation

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Figure 2.2 Reference Types
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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

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Figure 2.3 The Letters JEANS Stored bya Java
Program
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Escape Sequences

• The backslash (\) character causes Java to
  interpret the character that follows differently
• \b move back one space
• \f move to the next page
• \n move to the next line
• \r carriage return
• \t move to the next tab setting
• \\ backslash character output
• \ single quote output
• \ double quote output

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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

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Figure 2.8 An Example of a Value Stored in a
Reference Variable
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Figure 2.9a Creating a Reference Variable
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Figure 2.9b Instantiating an Object
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Figure 2.10 The Location of Different Strings
Using the Same Reference Variable
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LoanCalculator.java

• / File LoanCalculator.java
• Sample loan calculation program written in plain
  Java
• by Bruce Haft ltltlt for Extra credit submission
  PUT YOUR NAME HERE
• February 20, 2006 ltltlt 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

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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(Sys
  tem.in)
• // needed to use readLine()
• BufferedReader br new BufferedReader(isr)

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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)

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Next Week

• Finish Chapter 2
• Start Chapter 3
• All Extra Credit due by 3/13

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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))