Currency Converter
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ProblemThis program will convert dollar amounts from Canadian to US dollars, and vice versa. There will be
three input dialog boxes, implemented using JOptionPane.showInputDialog. The first input will ask
the user for the currency to which they would like to convert, either CAD or USD. The next input
asks for the current conversion rate to the desired currency, and the final input asks for the
dollar amount to be converted. The program will then display a dialog box with the dollar amounts
in both the original currency and the new currency.
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SolutionFirst we declare the variables we will need to solve the problem. //declare the variables String currencyTo; String currencyFrom; String input; double amount = 0; double newAmount = 0; double CADtoUSD; double USDtoCAD; boolean done = false; Next, we open the main while loop. The program will continue to run until the user clicks Cancel on
one of the input dialog boxes.
while(!done) { //all of the code will go in here } The first input from the user will be the currency that they want to convert to. Since we are only converting between two currencies, the other currency will obviously be the one we are converting from. Note that if currency is null, the program will not enter this section of code. If the user entered something other than "CAD" or "USD", we will keep looping until one of these two values is entered. //get the currency to which we will be converting currencyTo = JOptionPane.showInputDialog("Enter the currency you are converting to " + "- type either CAD or USD:"); if(currencyTo != null) { while(!currencyTo.equals("CAD") && !currency.equals("USD")) { currencyTo = JOptionPane.showInputDialog("Enter the currency you are converting to " + "- type either CAD or USD:"); } Next we will get the current conversion rate from the user. Although we could just hard code this into the program by initializing the conversion rate variables, doing it this way makes the program more flexible. //get the current rate if(currencyTo.equals("CAD")) { input = JOptionPane.showInputDialog("Enter the current USD to CAD conversion rate"); if(input != null) { USDtoCAD = Double.parseDouble(input); } } else //currency is USD { input = JOptionPane.showInputDialog("Enter the current CAD to USD conversion rate"); if(input != null) { CADtoUSD = Double.parseDouble(input); } } Now we will get the user to enter the amount they wish to convert, making sure that the amount they enter is not null and that it is greater than or equal to zero. Notice that we must convert input from a string to a double on each iteration, otherwise we will get an error in the second loop condition when we try to compare mismatched data types. //get an amount to convert input = JOptionPane.showInputDialog("Enter the dollar amount to be converted."); while(input == null The final step is to perform the conversion and print the result. //perform the conversion if(currencyTo.equals("CAD")) { newAmount = amount * USDtoCAD; currencyFrom = "USD"; } else { newAmount = amount * CADtoUSD; currencyFrom = "CAD"; } //print the result JOptionPane.showMessageDialog("$" + amount + " " + currencyFrom + " = $" + newAmount + " " + currencyTo); | ||
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