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CS1101X: Programming Methodology Recitation 1 Java Basics Numerical Data

CS1101X: Programming Methodology Recitation 1 Java Basics Numerical Data. Problem Statement. Problem statement: Write a program that asks for the user’s first, middle, and last names and replies with their initials. Example: input: Andrew Lloyd Weber output: ALW. Overall Plan.

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CS1101X: Programming Methodology Recitation 1 Java Basics Numerical Data

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  1. CS1101X: Programming MethodologyRecitation 1 Java Basics Numerical Data

  2. Problem Statement • Problem statement: Write a program that asks for the user’s first, middle, and last names and replies with their initials. Example: input: Andrew Lloyd Weber output: ALW

  3. Overall Plan • Identify the major tasks the program has to perform. • We need to know what to develop before we develop! • Tasks: • Get the user’s first, middle, and last names • Extract the initials and create the monogram • Output the monogram

  4. Development Steps • We will develop this program in two steps: • Start with the program template and add code to get input • Add code to compute and display the monogram

  5. Step 1: Design • The program specification states “get the user’s name” but doesn’t say how. • We will consider “how” in the Step 1 design • We will use JOptionPane for input • Input Style Choice #1 Input first, middle, and last names separately • Input Style Choice #2 Input the full name at once • We choose Style #2 because it is easier and quicker for the user to enter the information

  6. Step 1: Code /* Chapter 2 Sample Program: Displays the Monogram File: Step1/Ch2Monogram.java */ import javax.swing.*; class Ch2Monogram { public static void main (String[ ] args) { String name; name = JOptionPane.showInputDialog(null, "Enter your full name (first, middle, last):"); JOptionPane.showMessageDialog(null, name); } }

  7. Step 1: Test • In the testing phase, we run the program and verify that • we can enter the name • the name we enter is displayed correctly

  8. Step 2: Design (1/2) • Our programming skills are limited, so we will make the following assumptions: • input string contains first, middle, and last names • first, middle, and last names are separated by single blank spaces • Examples John Quincy Adams (okay) John Kennedy(not okay) Harrison, William Henry(not okay)

  9. “Aaron Ben Cosner” “Ben Cosner” “Aaron” “Cosner” “Ben” “ABC” Step 2: Design (2/2) • Given the valid input, we can compute the monogram by • breaking the input name into first, middle, and last • extracting the first character from them • concatenating three first characters

  10. Step 2: Code (1/2) /* Chapter 2 Sample Program: Displays the Monogram File: Step 2/Ch2MonogramStep2.java */ import javax.swing.*; class Ch2Monogram { public static void main(String[ ] args) { String name, first, middle, last, space, monogram; space = " "; //Input the full name name = JOptionPane.showInputDialog(null, "Enter your full name (first, middle, last):");

  11. Step 2: Code (2/2) //Extract first, middle, and last names first = name.substring(0, name.indexOf(space)); name = name.substring(name.indexOf(space)+1, name.length()); middle = name.substring(0, name.indexOf(space)); last = name.substring(name.indexOf(space)+1, name.length()); //Compute the monogram monogram = first.substring(0, 1) + middle.substring(0, 1) + last.substring(0,1); //Output the result JOptionPane.showMessageDialog(null, "Your monogram is " + monogram); } }

  12. Step 2: Test • In the testing phase, we run the program and verify that, for all valid input values, correct monograms are displayed. • We run the program numerous times. Seeing one correct answer is not enough. We have to try out many different types of (valid) input values.

  13. Program Review • The work of a programmer is not done yet. • Once the working program is developed, we perform a critical review and see if there are any missing features or possible improvements • One suggestion • Improve the initial prompt so the user knows the valid input format requires single spaces between the first, middle, and last names

  14. Problem Statement • Problem statement: Write a loan calculator program that computes both monthly and total payments for a given loan amount, annual interest rate, and loan period.

  15. Overall Plan • Tasks: • Get three input values: loanAmount, interestRate, and loanPeriod. • Compute the monthly and total payments. • Output the results.

  16. Required Classes

  17. Development Steps • We will develop this program in four steps: • Start with code to accept three input values. • Add code to output the results. • Add code to compute the monthly and total payments. • Update or modify code and tie up any loose ends.

  18. Step 1 Design • Call the showInputDialog method to accept three input values: • loan amount, • annual interest rate, • loan period. • Data types are

  19. Step 1 Code (1/2) • Directory: Chapter3/Step1 • Source File: Ch3LoanCalculator.java Program source file is too big to list here. From now on, we ask you to view the source files using your Java IDE.

  20. Step 1 Code (2/2) import javax.swing.*; class Ch3LoanCalculator { public static void main (String[] args) { double loanAmount, annualInterestRate; int loanPeriod; String inputStr; //get input values inputStr = JOptionPane.showInputDialog(null, "Loan Amount (Dollars+Cents):"); loanAmount = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Annual Interest Rate (e.g., 9.5):"); annualInterestRate = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Loan Period - # of years:"); loanPeriod = Integer.parseInt(inputStr); //echo print the input values System.out.println("Loan Amount: $" + loanAmount); System.out.println("Annual Interest Rate: " + annualInterestRate + "%"); System.out.println("Loan Period (years): " + loanPeriod); } }

  21. Step 1 Test • In the testing phase, we run the program multiple times and verify that • we can enter three input values • we see the entered values echo-printed correctly on the standard output window

  22. Step 2 Design • We will consider the display format for out. • Two possibilities are (among many others)

  23. Step 2 Code (1/3) • Directory: Chapter3/Step2 • Source File: Ch3LoanCalculator.java

  24. Step 2 Code (2/3) import javax.swing.*; class Ch3LoanCalculator { public static void main (String[] args) { double loanAmount, annualInterestRate; double monthlyPayment, totalPayment; int loanPeriod; String inputStr; //get input values inputStr = JOptionPane.showInputDialog(null, "Loan Amount (Dollars+Cents):"); loanAmount = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Annual Interest Rate (e.g., 9.5):"); annualInterestRate = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Loan Period - # of years:"); loanPeriod = Integer.parseInt(inputStr);

  25. Step 2 Code (3/3) //compute the monthly and total payments monthlyPayment = 132.15; totalPayment = 15858.10; //display the result System.out.println("Loan Amount: $" + loanAmount); System.out.println("Annual Interest Rate: " + annualInterestRate + "%"); System.out.println("Loan Period (years): " + loanPeriod); System.out.println("\n"); //skip two lines System.out.println("Monthly payment is $ " + monthlyPayment); System.out.println(" TOTAL payment is $ " + totalPayment); } }

  26. Step 2 Test • We run the program numerous times with different types of input values and check the output display format. • Adjust the formatting as appropriate

  27. Step 3 Design • The formula to compute the geometric progression is the one we can use to compute the monthly payment. • The formula requires the loan period in months and interest rate as monthly interest rate. • So we must convert the annual interest rate (input value) to a monthly interest rate (per the formula), and the loan period to the number of monthly payments.

  28. Step 3 Code (1/3) • Directory: Chapter3/Step3 • Source File: Ch3LoanCalculator.java

  29. Step 3 Code (2/3) import javax.swing.*; class Ch3LoanCalculator { public static void main (String[] args) { final int MONTHS_IN_YEAR = 12; double loanAmount, annualInterestRate; double monthlyPayment, totalPayment, monthlyInterestRate; int loanPeriod, numberOfPayments; String inputStr; //get input values inputStr = JOptionPane.showInputDialog(null, "Loan Amount (Dollars+Cents):"); loanAmount = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Annual Interest Rate (e.g., 9.5):"); annualInterestRate = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Loan Period - # of years:"); loanPeriod = Integer.parseInt(inputStr);

  30. Step 3 Code (3/3) //compute the monthly and total payments monthlyInterestRate = annualInterestRate / MONTHS_IN_YEAR / 100; numberOfPayments = loanPeriod * MONTHS_IN_YEAR; monthlyPayment = (loanAmount * monthlyInterestRate) / (1 - Math.pow(1/(1 + monthlyInterestRate), numberOfPayments ) ); totalPayment = monthlyPayment * numberOfPayments; //display the result System.out.println("Loan Amount: $" + loanAmount); System.out.println("Annual Interest Rate: " + annualInterestRate + "%"); System.out.println("Loan Period (years): " + loanPeriod); System.out.println("\n"); //skip two lines System.out.println("Monthly payment is $ " + monthlyPayment); System.out.println("TOTAL payment is $ " + totalPayment); } }

  31. Step 3 Test • We run the program numerous times with different types of input values and check the results.

  32. Step 4 Finalize • We will add a program description • We will format the monthly and total payments to two decimal places using DecimalFormat. Directory: Chapter3/Step4 Source File: Ch3LoanCalculator.java

  33. Step 4 Code (1/3) import javax.swing.*; import java.text.*; class Ch3LoanCalculator { public static void main (String[] args) { final int MONTHS_IN_YEAR = 12; double loanAmount, annualInterestRate, monthlyPayment, totalPayment, monthlyInterestRate; int loanPeriod, numberOfPayments; String inputStr; DecimalFormat df = new DecimalFormat("0.00"); //describe the program System.out.println("This program computes the monthly and total"); System.out.println("payments for a given loan amount, annual"); System.out.println("interest rate, and loan period."); System.out.println("Loan amount in dollars and cents, e.g., 12345.50"); System.out.println("Annual interest rate in percentage, e.g., 12.75"); System.out.println("Loan period in number of years, e.g., 15"); System.out.println("\n"); //skip two lines

  34. Step 4 Code (2/3) //get input values inputStr = JOptionPane.showInputDialog(null, "Loan Amount (Dollars+Cents):"); loanAmount = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Annual Interest Rate (e.g., 9.5):"); annualInterestRate = Double.parseDouble(inputStr); inputStr = JOptionPane.showInputDialog(null, "Loan Period - # of years:"); loanPeriod = Integer.parseInt(inputStr); //compute the monthly and total payments monthlyInterestRate = annualInterestRate / MONTHS_IN_YEAR / 100; numberOfPayments = loanPeriod * MONTHS_IN_YEAR; monthlyPayment = (loanAmount * monthlyInterestRate) / (1 - Math.pow(1/(1 + monthlyInterestRate), numberOfPayments ) ); totalPayment = monthlyPayment * numberOfPayments;

  35. Step 4 Code (3/3) //display the result System.out.println("Loan Amount: $" + loanAmount); System.out.println("Annual Interest Rate: " + annualInterestRate + "%"); System.out.println("Loan Period (years): " + loanPeriod); System.out.println("\n"); //skip two lines System.out.println("Monthly payment is $ " + df.format(monthlyPayment)); System.out.println("TOTAL payment is $ " + df.format(totalPayment)); } }

  36. End of Recitation #1

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