Question

JAVA

Overview

This program implements a simple, interactive calculator.

Major topics

• writing a program from scratch
• multiple methods
• testing

In this document

• program logic & program structure (class, methods, variables)
• input / output
• assumptions and limitations
• documentation & style
• suggested schedule
• cover letter discussion questions
• grading, submission, and due date
• additional notes
• challenges
• sample output
• test plan

Program Logic

• The program prompts the user to select a type of math problem (addition, subtraction, multiplication, or division), enter the two operands, then calculates and outputs the answer.
• The program runs until the user does not want to do any more problems.
• A final tally of problems is printed at the end.

Program Structure and Data

                                                   Calculator class

Constructor printIntro method calculate method printReport method main method

• one class named FirstnameLastname_02_CS1Calculator
• methods: use the method descriptions as English comments in the code, laying out each logic step to be written in Java
  • main: calls constructor, printIntro, calculate, print report
  • constructor: initializes counters to zero, instantiates and initializes a Scanner to read from the keyboard
  • printIntro method: explains program to user
  • calculate method: primary method with a loop until the user is done
    • run a while loop until the user doesn't want to do another problem
      • display operation choices
      • get user choice, echo their choice (print it back on the screen)
        • use if-elses for which operation to print
      • get operands (numbers to use in the math problem)
      • calculate and print answer
        • use if-elses to pick which math formula
      • count operation type (addition, etc.)
        • use if-elses to pick which counter to increment
      • ask if the user wants to do another problem
    • calculate total problems done (addition count + subtraction count + …)
  • printReport method
    • outputs total of each problem done and overall total problems (see sample output)
• instance (class level) data
  • a Scanner (needs an import statement)
  • 4 ints to count the number of each problem type (addition, etc.)
  • 1 int to hold total problem count
• local variables: as needed in each method (perhaps none in some methods)

I/O

• interactive only (keyboard & screen), no data files
• input
  • user
    • enters the type of problem (addition, etc.)
    • enters two numbers for each calculation
    • enters the decision whether to do more problems
  • the user may enter either uppercase or lowercase for the continuation answer and the problem type selection
  • reading numbers: all input is String type, so it must be converted to int using a parser method from the Integer class:

firstOperand = scan.nextLine();

firstNumber = Integer.parseInt(firstOperand);

• output (see sample output later in this document)
  • directions to the user about the problem
  • prompts to choose problem type and to enter numbers
  • calculated answer to the math problem
  • summary of problem types completed

Assumptions & Limitations

• integers only (no real numbers)
• input numbers and answers will fit in the range of the int data type
• division is integer division
• binary operations only (two operands)
• addition, subtraction, multiplication, division and exit are the only operations supported
• perfect user: all input will be correct (y or n only; integers only for operands)
• results are not saved
• the user will do at least one problem

Test Plan

• Run the following test data, divided into sessions so that total problem counts can be checked. Restart the program to run each session (set of multiple, related problems). Be sure to check that each result is correct.

• Simple basic problems, all operations
  • test 1: 111 + 222 = 333
  • test 2: 9999 + 8888 = 18887
  • test 3: 83 / 83 = 1
  • test 4: 84 / 83 = 1
  • test 5: 83 / 84 = 0
  • test 6: 0 – 0 = 0
  • test 7: 500000 + 500001 = 10000001
  • totals
    • Addition problems: 3
    • Subtraction problems: 1
    • Multiplication problems: 0
    • Division problems: 3
    • Total problems: 7

Note: no tests for bad data since this program is guaranteed a perfect user (i.e., no bad input).

Further work / challenges For any you do, run additional test cases to check the new functionality.

• Add the modulus (remainder) function as a fifth choice for the user. Include a counter for "mod" problems. The math symbol for mod is % (but it does not do anything related to percentage).
• Experiment with the NumberFormat class to learn how to place commas in results larger than 999 and include that for answers before they are printed.
• Instead of printing "The answer is", print the result in math format:

3 + 12 = 15

• Print totals for each type only if the user did any of that type. For example, if they did not do any subtraction problems, don't print the report line listing zero subtraction problems. Use if statements to control printing or not, by looking at the counter for that problem type.

Discussion Questions (cover letter)

1. Overflow. Find out what happens when you try to add two numbers whose sum exceeds the maximum integer value (just over two billion, one hundred million). Test two billion plus two billion. What result did you get? Explain why overflow happens on a computer.
2. Explain inexact results on integer division such as:

2 / 5 = 0 and 51 / 25 = 2

3. What syntax (Java grammar rules) did you have the most trouble getting right?
4. What semantics (meaning of the code) did you have the most trouble understanding?

Answer 1

Program:

import java.util.Scanner;
class Calculator
{
int a,s,m,d;
  
// Constructor
public Calculator()
{
a=0;
s=0;
m=0;
d=0;
}
  
// printIntro Method For Description
public void printIntro()
{
System.out.println("********** Simple Calculator **********");
System.out.println("1 -> Addition");
System.out.println("2 -> Substratcion");
System.out.println("3 -> Multiplication");
System.out.println("4 -> Division");
}
  
// Calculate Method to perform Operations(+,-,*,/)
public void calculate()
{
String option;
int choice,num1,num2;
  
Scanner input = new Scanner(System.in);
  
do{
printIntro();
  
System.out.println("Enter your Choice:");
choice = input.nextInt();
  
System.out.println("Enter Number 1:");
num1 = input.nextInt();
  
System.out.println("Enter Number 2:");
num2 = input.nextInt();
  
if(choice == 1)
{
System.out.println(num1+" + "+num2+" = "+(num1+num2));
a++;
}
else if(choice == 2)
{
System.out.println(num1+" - "+num2+" = "+(num1-num2));
s++;
}
else if(choice == 3)
{
System.out.println(num1+" * "+num2+" = "+(num1*num2));
m++;
}
else if(choice == 4)
{
System.out.println(num1+" / "+num2+" = "+(num1/num2));
d++;
}
else
{
System.out.printf("\nYou have entered wrong option\n");
}
  
System.out.println("Do you want to perform Another Operation. Press Y to continue:");
option = input.next();
  
}while(option.equals("y") || option.equals("Y"));
  
printReport(a,s,m,d);
}
  
// printReport Method to print the Detailed report
public void printReport(int a,int s,int m,int d)
{
System.out.println("Addition Problems: "+a);
System.out.println("Substratcion Problems: "+s);
System.out.println("Multiplication Problems: "+m);
System.out.println("Division Problems: "+d);
}
  
}

// Driver Class

class FirstnameLastname_02_CS1Calculator.{
  
public static void main(String[] args) {
  
Calculator c = new Calculator();
  
c.calculate();
}
}

Note: Refer the Screenshots for further Clarification