Question

this is for java class

Define a utility class for displaying values of type double. Call the class DoubleOut. Include all the methods from the class DollarFormat in Listing 6.14, all the methods from the class OutputFormat of Self-Test Question 30, and a method called scienceWrite that displays a value of type double using e notation, such as 2.13e–12. (This e notation is also called scientific notation, which explains the method name.) When displayed in e notation, the number should appear with exactly one nonzero digit before the decimal point—unless the number is exactly zero. The method scienceWrite will not advance to the next line. Also add a method called scienceWriteln that is the same as scienceWrite except that it does advance to the next line. All but the last two method definitions can simply be copied from the text (or more easily from the source code for this book that is available on the Web.). Note that you will be overloading the method names write and writeln.
Write a driver program to test your method scienceWriteln. This driver program should use a stub for the method scienceWrite. (Note that this means you can write and test scienceWriteln before you even write scienceWrite.) Then write a driver program to test the method scienceWrite. Finally, write a program that is a sort of super driver program that takes a double value as input and then displays it using the two writeln methods and the scienceWriteln method. Use the number 5 for the number of digits after the decimal point when you need to specify such a number. This super driver program should allow the user to repeat this testing with additional numbers of type double until the user is ready to end the program.

Listing 6.14 The Corrected Class DollarFormat
public class DollarFormat
{
/**
Displays amount in dollars and cents notation.
Rounds after two decimal places.
Does not advance to the next line after output.
*/
public static void write(double amount)
{
if (amount >= 0)
{
System.out.print('$');
writePositive(amount);
}
else
{
double positiveAmount = amount;
System.out.print('$');   
System.out.print('-');   
writePositive(positiveAmount);
}
}
//Precondition: amount >= 0;
//Displays amount in dollars and cents notation. Rounds
//after two decimal places. Omits the dollar sign.
private static void writePositive(double amount)
{
int allCents = (int)(Math.round(amount * 100));
int dollars = allCents / 100;
int cents = allCents % 100;
System.out.print(dollars);
System.out.print('.');
if (cents < 10)   
System.out.print('0');
System.out.print(cents);
}
/**
Displays amount in dollars and cents notation.
Rounds after two decimal places.
Advances to the next line after output.
*/
public static void writeln(double amount)
{
write(amount);
System.out.println();
}
}

are there supposed to be different java files? how are they supposed to look?

thanks!

Answer 1

import java.util.Scanner;

public class DollarFormat {
  
/**
Displays amount in dollars and cents notation.
Rounds after two decimal places.
Does not advance to the next line after output.
*/
public static void write(double amount)
{
if(amount >= 0)
{
System.out.print('$');
writePositive(amount);
}
else
{
double positiveAmount = (amount * -1);
System.out.print('$');   
System.out.print('-');   
writePositive(positiveAmount);
}
}
  
//Precondition: amount >= 0;
//Displays amount in dollars and cents notation. Rounds
//after two decimal places. Omits the dollar sign.
public static void writePositive(double amount)
{
int allCents = (int)(Math.round(amount * 100));
int dollars = allCents / 100;
int cents = allCents % 100;
System.out.print(dollars);
System.out.print('.');
if (cents < 10)   
System.out.print('0');
System.out.print(cents);
}
  
/**
Displays amount in dollars and cents notation.
Rounds after two decimal places.
Advances to the next line after output.
*/
public static void writeln(double amount)
{
write(amount);
System.out.println();
}
  
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
char yesNo;
  
do
{
System.out.print("Please enter an amount: $");
double amount = Double.parseDouble(sc.nextLine().trim());
System.out.print("Result: ");
writeln(amount);
  
System.out.print("Continue? [Y/N]: ");
yesNo = sc.nextLine().charAt(0);
System.out.println();
if(yesNo == 'N' || yesNo == 'n')
{
System.out.println("Thank you..Goodbye!\n");
System.exit(0);
}
}while(yesNo != 'N' || yesNo != 'n');
}
}

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