Manipulating Data Using Methods - Java Programming: Comprehensive Concepts and Techniques - page 213

Table 3-21 Kilowatt Applet Constructed Components

OBJECT IDENTIFIER METHOD PARAMETER (CAPTION OR LENGTH)

Label welcome Welcome to the Appliance Energy Calculator

Label costKwhrLabel Please enter the cost per kilowatt-hour in cents:

TextField costKwhrField 5

Label hoursPerYearLabel Please enter the kilowatt-hours consumed:

TextField hoursPerYearField 5

Button calcButton Calculate

Label outputLabel Click the Calculate button to display the

average energy cost.

6. Create an init() method to add all of the above components to the applet
interface.
7. Enter the code to add the ActionListener to the calcButton and close the
init() method with a brace.
8. Create an actionPerformed() method to convert the input and perform the
calculations. Enter the code to get the text from each text box, parse it, and
assign it to the appropriate declared variable as shown in Table 3-22.

Table 3-22 KilowattApplet Construction and Conversion Code

double costKwhr = Double.parseDouble(costKwhrField.getText());
double kwHours = Double.parseDouble(hoursPerYearField.getText());

9. Declare a double variable named average.
10. Write a line of code to perform the calculation that multiplies the cents by
the kilowatt-hours in a year and then assigns it to the variable, average.
11. Enter the code from Table 3-23 to round the average with the Math.round()
method and assign it to the text of the output label. The Math.round()
method includes a casting of the literal 100 to double in order to retain the
decimal places.

Table 3-23 KilowattApplet Output Code

outputLabel.setText(“The average annual cost to operate this appliance is $” +
Math.round(average* 100)/100D);

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