Chapter 8

Fill in the blanks in each of the following statements: a) When compiling a class in a package, the javac command-line option_______ specifies where to store the package and causes the compiler to create the package's directories if they do not exist. b) \(\operatorname{sering}\) class static method ________ is similar to method System.out.printf, but returns a formatted String rather than displaying a String in a command window. c) If a method contains a local variable with the same name as one of its class's fields, the local variable _______ the field in that method's scope. d) The_______ method is called by the garbage collector just before it reclaims an object's memory. e) \(\mathrm{A}(\mathrm{n}) \)______ declaration specifies one class to import. f) If a class declares constructors, the compiler will not create a(n) ___________ . g) An object's ___________ method is called implicitly when an object appears in code where a String is needed. h) Get methods are commonly called___________ or __________. i) \(A(n)\)____________ method tests whether a condition is true or false. j) For every enum, the compiler generates a static method called ___________ that returns an array of the enum's constants in the order in which they were declared. k) Composition is sometimes referred to as a(n)_______ relationship. I) \(A(n)\) ___________ declaration contains a comma-separated list of constants. \(\mathrm{m}\) ) \(\mathrm{A}(\mathrm{n}) \) __________ variable represents classwide information that is shared by all the objects of the class. n) \(A(n) \) _______________declaration imports one static member. o) The ___________ states that code should be granted only the amount of privilege and access that the code needs to accomplish its designated task. p) Keyword __________ specifies that a variable is not modifiable. q) \(A(n)\)________ consists of a data representation and the operations that can be performed on the data. r) There can be only one __________ in a Java source-code file, and it must precede all other declarations and statements in the file. s) \(\mathrm{A}(\mathrm{n})\) _______ declaration imports only the classes that the program uses from a particular package. t) The compiler uses a(n) _____________ to locate the classes it needs in the classpath. u) The classpath for the compiler and \(\mathrm{JVM}\) can be specified with the__________ option to the javac or java command, or by setting the ___________ environment variable. v) Set methods are commonly called __________ because they typically change a value. w) \(A(n)\) _____________ imports all static members of a class. x) The public methods of a class are also known as the class's __________ or _________ . y) System class static method __________ indicates that the garbage collector should make best-cffort attempt to reclaim objects that are eligible for garbage collection. z) An object that contains ________ has data values that are always kept in range.

Explain the notion of package access in Java. Explain the negative aspects of package access.

What happens when a return type, even void, is specified for a constructor?

(Rectangle Class) Create a class Rectangle. The class has attributes length and width, each of which defaults to \(1 .\) It has methods that calculate the perimeter and the area of the rectangle. It has set and get methods for both Tength and width. The set methods should verify that 7 ength and width are each floating-point numbers larger than 0.0 and less than \(20.0 .\) Write a program to test class Rectangle.

\((\)Savings Account Class) Create class SavingsAccount. Use a static variable annual Inter- estRate to store the annual interest rate for all account holders. Each object of the class contains a private instance variable savingsBal ance indicating the amount the saver currently has on deposit. Provide method calculateMonth1yInterest to calculate the monthly interest by multiplying the savingsBalance by annual InterestRate divided by 12 - this interest should be added to savingsBalance. Provide a static method modifyInterestRate that sets the annual InterestRate to a new value. Write a program to test class SavingsAccount. Instantiate two savingsAccount objects, saver1 and saver2, with balances of \(\$ 2000.00\) and \(\$ 3000.00,\) respectively. Sct annual InterestRate to \(4 \%,\) then calculate the monthly interest and print the new balances for both savers. Then set the annual InterestRate to \(5 \%\), calculate the next month's interest and print the new balances for both savers.

\((\text { Enhancing Class Date})\) Modify class Date of Fig. 8.7 to perform error checking on the initializer values for instance variables month, day and year (currently it validates only the month and day). Provide a method nextDay to increment the day by one. The Date object should always remain in a consistent state. Write a program that rests the nextDay method in a loop that prints the date during each iteration of the loop to illustrate that the nextDay method works correctly. Test the following cases: a) incrementing into the next month and b) incrementing into the next year.

(Returning Error Indicators from Metbods) Modify the set methods in class Time2 of Fig. 8.5 to return appropriate error values if an attempt is made to set one of the instance variables hour, minute or second of an object of class Time to an invalid value. [Hint: Use boolean return types on cach method.] Write a program that tests these new set methods and outputs error messages when incorrect values are supplied.

Write an enum type TrafficLight, whose constants (RED, GREEN, YELLOW) take one parameter - the duration of the light. Write a program to test the TrafficLight enum so that it displays the enum constants and their durations.

\((\) Complex Numbers) Create a class called Complex for performing arithmetic with complex numbers. Complex numbers have the form \\[ \text {reallart }+\text { imaginaryPart }^{*} \\] where \(i\) is \\[ \sqrt{-1} \\] Write a program to test your class. Use floating-point variables to represent the private data of the class. Provide a constructor that enables an object of this class to be initialized when it is declared. Provide a no-argument constructor with default values in case no initializers are provided. Provide public methods that perform the following operations: a) Add two Complex numbers: The real parts are added together and the imaginary parts are added together. b) Subtract two Complex numbers: The real part of the right operand is subtracted from the real part of the left operand, and the imaginary part of the right operand is subtracted from the imaginary part of the left operand. c) Print Complex numbers in the form (a, b), where a is the real part and b is the imaginary part.

(Date Class) Create class Date with the following capabilities: a) Output the date in multiple formats, such as MM/DD/YYYY June \(14, \quad 1992\) DDD YYYY b) Use overloaded constructors to create Date objects initialized with dates of the formats in part (a). In the first case the constructor should receive three integer values. In the second case it should receive a String and two integer values. In the third case it should receive two integer values, the first of which represents the day number in the year. \([\text {Hint: }\) To convert the string representation of the month to a numeric value, compare strings using the equals method. For example, if \(s 1\) and \(s 2\) are strings, the method call s1.equals \((s 2)\) returns true if the strings are identical and otherwise returns false.