CS1101: Programming Methodology Recitation 2

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CS1101 Programming MethodologyRecitation 2
Java Basics
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Problem Solving Process
Determine problem features e.g. input, output
Analysis
Describe objects and methods
Design
Produce the classes and code
Implementation
Testing
Examine for correctness
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Case Study 1

• Objective Develop a program AverageFive.java
  that computes the average of 5 integer inputs.
• Analysis and Design
• Constants
• LIST_SIZE int //number of input values(5)
• Variables
• currentInput int //variable to hold current
  input value
• runningTotal int //variable to hold sum of input
  value
• //initialize to 0
• average int //variable to hold ave of input
  values
• Objects
• stdin references a BufferedReader object
  associated with the standard input stream
  System.in

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Analysis and Design 4. Methods method main()
step 1. define necc data structures.
step 2. process inputs to determine input
total. step 3. compute average.
step 4. display average.
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// Purpose Average five user integer
inputs import java.io. public class
AverageFive // main() application entry
point public static void main(String args)
throws IOException // define necessary data
structures (Step 1) final int LIST_SIZE 5
// number of inputs to process int
currentInput // current input
value int runningTotal 0 // sum of
inputs processed so far BufferedReader stdin
// input stream new BufferedReader(new
InputStreamReader(System.in))
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// process inputs to determine input total
(Step 2) System.out.print("Enter an integer
number ") currentInput Integer.parseInt(std
in.readLine()) runningTotal
currentInput System.out.print("Enter an
integer number ") currentInput
Integer.parseInt(stdin.readLine()) runningTota
l currentInput System.out.print("Enter
an integer number ") currentInput
Integer.parseInt(stdin.readLine()) runningTota
l currentInput System.out.print("Enter
an integer number ") currentInput
Integer.parseInt(stdin.readLine()) runningTota
l currentInput System.out.print("Enter
an integer number ") currentInput
Integer.parseInt(stdin.readLine()) runningTota
l currentInput
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// compute average (Step 3) int average
runningTotal / LIST_SIZE // display
average (Step 4) System.out.println("The input
average is " average)
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Use of Iterative Constructs // Compute average
of a list of positive numbers import
java.io. public class NumberAverage //
main() application entry point public static
void main(String args) throws IOException
// set up the list processing BufferedRea
der stdin new BufferedReader( new
InputStreamReader( System.in ) ) int
valuesProcessed 0 // no values processed so
far double valueSum 0 // running
total
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Use of Iterative Constructs // prompt user
for values System.out.println("Enter positive
numbers one per line. " "Indicate the end
of the list with a negative number.") //
get first value double value
Double.parseDouble(stdin.readLine()) //
process values one-by-one while (value gt 0)
// add value to running total valueSum
value // processed another
value valuesProcessed // prepare for
next iteration --- get next value value
Double.parseDouble(stdin.readLine())
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Use of Iterative Constructs // display
result if (valuesProcessed gt 0) //
compute and display average double average
valueSum / valuesProcessed System.out.println
("Average " average) else
System.out.println("No list to
average")
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Case Study 2
Objective Develop an interactive program that
converts a data in American format (August 12,
2004) to the international format
(2004-August-12) Analysis and Design
Objects stdin BufferedReader //standard
input stream buffer String //represent input
date in American formatmonth String //represent
the month day String //represent the day of
the month year String //represent the
year standardDate String //represent the date
in standard format
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Analysis and Design Algorithm step 1.
display purpose of program. step 2. issue
prompt for user to enter date in American
format step 3. get a String representation of
the date from input and assign to variable
buffer. step 4. echo buffers date
representation step 5. examine buffers date
representation and extract a String
representation of the input month. step 6.
examine buffers date representation and extract
a String representation of the input
day. step 7. examine buffers date
representation and extract a String
representation of the input year. step 8.
assign to variable standardDate the String
concatenation of year, month, and day
with separating hyphens step 9. display
standardDate
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// Convert user-specified date from American to
standard format import java.io. class
DateTranslation // main() application
entry point static public void main(String
args) throws IOException // produce a
legend (Step 1) System.out.println("Date
format translator") System.out.println("
Converts a date from an American" " format
(e.g., July 4, 1776)") System.out.println("
to standard format (e.g.," "
1776-July-4).") System.out.println() //
prompt the user for a date in American format
(Step 2) System.out.print("Enter a date in
American format ")
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// acquire the input entered by the user
(Step 3) BufferedReader stdin new
BufferedReader( new InputStreamReader(System.i
n) ) String buffer stdin.readLine().trim()
// echo the input back (Step 4)
System.out.println("The translation
of") System.out.println(" "
buffer) // get month entered by the user
(Step 5) int m buffer.indexOf("
") String month buffer.substring(0,
m) buffer buffer.substring(m1).trim()
// get day entered by the user (Step 6) int
n buffer.indexOf(",") String day
buffer.substring(0, n) buffer
buffer.substring(n1).trim() // get year
entered by the user (Step 7) String year
buffer
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// create standard format version of
input (Step 8) String standardDate year
"-" month "-" day // display the
translation (Step 9) System.out.println("to
standard format is") System.out.println(" "
standardDate)
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buffer buffer.trim() //trim any leading and
trailing white space
Int m buffer.indexOf ( ) //find the
first blank String month buffer.substring(0,m)
//copy the string from position 0 to m-1
in buffer to month
buffer buffer.substring(m1).trim()
month
Int n buffer.indexOf (, ) //find the
comma String day buffer.substring(0,m)
//copy the string from position 0 to n-1
in buffer to day
buffer buffer.substring(n1).trim()
day
String year buffer //get year
year
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Case Study 2
Sample Output Date format translator Converts
a date from American format (e.g. August 12,
2004) to international format (e.g.
2004-August-12) Enter date in American format
September 15, 2000 The translation of
September 15, 2000 to standard format
is 2000-September-15