Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

72 Chapter 2 Elementary Programming
monthlyPayment
totalPayment
preparing output
30 // Calculate payment
31 double monthlyPayment = loanAmount * monthlyInterestRate / (1
32 – 1 / Math.pow(1 + monthlyInterestRate, numberOfYears * 12));
33 double totalPayment = monthlyPayment * numberOfYears * 12;
34
35 // Format to keep two digits after the decimal point
36 monthlyPayment = (int)(monthlyPayment * 100) / 100.0;
37 totalPayment = (int)(totalPayment * 100) / 100.0;
38
39 // Display results
40 String output = "The monthly payment is $" + monthlyPayment +
41 "\nThe total payment is $" + totalPayment;
42 JOptionPane.showMessageDialog(null, output );
43 }
44 }
The showInputDialog method in lines 6–7 displays an input dialog. Enter the interest
rate as a double value and click OK to accept the input. The value is returned as a string that
is assigned to the String variable annualInterestRateString. The
Double.parseDouble (annualInterestRateString) (line 11) is used to convert the
string into a double value.
JOptionPane or Scanner?
✓Point✓ Check
Pedagogical Note
For obtaining input you can use either JOptionPane or Scanner—whichever is
more convenient. For consistency and simplicity, the examples in this book use
Scanner for getting input. You can easily revise the examples using JOptionPane
for getting input.
2.34 Why do you have to import JOptionPane but not the Math class?
2.35 How do you prompt the user to enter an input using a dialog box?
2.36 How do you convert a string to an integer? How do you convert a string to a
double?
KEY TERMS
algorithm 34
assignment operator (=) 42
assignment statement 42
byte type 45
casting 56
char type 62
constant 43
data type 35
declare variables 35
decrement operator (– –) 54
double type 45
encoding 62
escape character 63
expression 42
final keyword 43
float type 45
floating-point number 35
identifier 40
increment operator (++) 54
incremental development
and testing 37
int type 45
IPO 39
literal 48
long type 45
narrowing (of types) 56
operands 46
operator 46
overflow 45
postdecrement 54
postincrement 54
predecrement 54
preincrement 54
primitive data type 35
pseudocode 34
requirements specification 58