OBJECTS AND CLASSES - Introduction to Java Programming: Comprehensive Version - page 361

*9.5

( Use the GregorianCalendar class ) Java API has the GregorianCalendar class
in the java.util package, which you can use to obtain the year, month, and day of a
date. The no-arg constructor constructs an instance for the current date, and the meth-
ods get(GregorianCalendar.YEAR) , get(GregorianCalendar.MONTH) ,
and get(GregorianCalendar.DAY_OF_MONTH) return the year, month, and day.
Write a program to perform two tasks:

Display the current year, month, and day.

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The GregorianCalendar class has the setTimeInMillis(long) , which
can be used to set a specified elapsed time since January 1, 1970. Set the value
to 1234567898765L and display the year, month, and day.

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Sections 9.7-9.9
*9.6

( Stopwatch ) Design a class named StopWatch . The class contains:

■ Private data fields startTime and endTime with getter methods.

■ A no-arg constructor that initializes startTime with the current time.

■ A method named start() that resets the startTime to the current time.

■ A method named stop() that sets the endTime to the current time.

■ A method named getElapsedTime() that returns the elapsed time for the
stopwatch in milliseconds.

Draw the UML diagram for the class and then implement the class. Write a test
program that measures the execution time of sorting 100,000 numbers using
selection sort.

9.7

( The Account class ) Design a class named Account that contains:

■ A private int data field named id for the account (default 0 ).

■ A private double data field named balance for the account (default 0 ).

A private double data field named annualInterestRate that stores the cur-
rent interest rate (default 0 ). Assume all accounts have the same interest rate.

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A private Date data field named dateCreated that stores the date when the
account was created.

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A no-arg constructor that creates a default account. ■

A constructor that creates an account with the specified id and initial balance.

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The accessor and mutator methods for id , balance , and annualInterestRate .

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The accessor method for dateCreated .

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A method named getMonthlyInterestRate() that returns the monthly
interest rate.

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A method named getMonthlyInterest() that returns the monthly interest.

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A method named withdraw that withdraws a specified amount from the
account.

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A method named deposit that deposits a specified amount to the account.
Draw the UML diagram for the class and then implement the class. ( Hint : The
method getMonthlyInterest() is to return monthly interest, not the interest rate.
Monthly interest is balance * monthlyInterestRate . monthlyInterestRate
is annualInterestRate / 12 . Note that annualInterestRate is a percentage,
e.g., like 4.5%. You need to divide it by 100.)
Write a test program that creates an Account object with an account ID of 1122,
a balance of $20,000, and an annual interest rate of 4.5%. Use the withdraw
method to withdraw $2,500, use the deposit method to deposit $3,000, and print
the balance, the monthly interest, and the date when this account was created.

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