Java programming homework # 5 and #6

Homework 5


1 What is the printout of running the class C (via the command “java C”) in the code below (saved in (And, is that what you expected?)

1: class A {

2: public A () {

3: System.out.println( “A’s no-arg constructor is invoked” );

4: }

5: }


7: class B extends A {

8: }


10: public class C {

11: public static void main ( String [] args ) {

12: B b = new B();

13: }

14: }

2 What problem do you expect to see if compiling the program below? What was the error(s), if any, actually produced?

1: class A {

2: public A ( int x ) {

3: }

4: }


6: class B extends A {

7: public B () {

8: }

9: }


11: public class C {

12: public static void main ( String [] args ) {

13: B b = new B();

14: }

15: }

3 Which of the follow statements are true? Which are false? Explain why.

A subclass is a subset of a superclass.

B When invoking a constructor from a subcass, its superclass’s no-arg constructor is always invoked.

C You can override a private method defined in a superclass.

D You can override a static method defined in a superclass.

4 What is the benefit of using the @Override annotation?

5 a Show the output of the following program:

1: public class Test {

2: public static void main ( String [] args ) {

3: A a = new A( 3 );

4: }

5: }


7: class A extends B {

8: public A ( int t ) {

9: System.out.println( “A’s constructor is invoked” );

10: }

11: }


13: class B {

14: public B () {

15: System.out.println( “B’s constructor is invoked” );

16: }

17: }

B Is the no-arg constructor of Object invoked when new A(3) is invoked?

6 Indicate true or false for the follow statements:

A You can always successfully cast an instance of a subclass to a superclass.

B You can always successfully cast an instance of a superclass to a subclass.

7 What’s wrong with the following code?

1: public class Test {

2: public static void main ( String [] args ) {

3: Object fruit = new Fruit();

4: Object apple = (Apple) fruit;

5: }

6: }


8: class Apple extends Fruit {

9: }


11: class Fruit {

12: }

8 When overriding the equals method, a common mistake is mistyping its signature in the subclass. For example, the equals method is incorrectly written as equals(Circle circle) as shown in (a) below. It should be written as equals(Object circle), as shown in (b) below. Show the output of running class Test using the Circle class first from (a), and then from (b). Explain the output.

1: public class Test {

2: public static void main ( String [] args ) {

3: Object circle1 = new Circle();

4: Object circle2 = new Circle();

5: System.out.println( circle1.equals( circle2 ) );

6: }

7: }

1: class Circle {

2: double radius;

3: public boolean equals ( Circle circle ) {

4: return this.radius == circle.radius;

5: }

6: }

1: class Circle {

2: double radius;

3: public boolean equals ( Object circle ) {

4: return this.radius == ((Circle) circle).radius;

5: }

6: }

Next, try adding the “@Override” annotation to the equals method in (a), and then try compiling. Repeat with (b). What are the results, and are they as you expected?

9 How would you prevent a class from being extended? How would you prevent a method from being overridden?

10 Which of the following classes define legal abstract classes?

A 1: class A {

2: abstract void unfinished ( ) {

3: }

4: }

B 1: public class abstract A {

2: abstract void unfinished ( ) {

3: }

4: }

C 1: class A {

2: abstract void unfinished ( ) ;

3: }

D 1: abstract class A {

2: protected void unfinished ( ) ;

3: }

E 1: abstract class A {

2: abstract void unfinished ( ) ;

3: }

F 1: class A {

2: abstract int unfinished ( ) ;

3: }

11 Suppose A is an interface. Can you create an instance using “new A()”?

12 Which of the following (if any) is a correct interface declaration? (Assume I1 and I2 are correctly defined elsewhere.)

A 1: interface A {

2: void print () {

3: };

4: }

B 1: abstract interface A extends I1, I2 {

2: abstract void print () {

3: };

4: }

C 1: abstract interface A {

2: print () ;

3: }

D 1: interface A {

2: void print () ;

3: }

Homework 6


1 How do you create a Date for the current time? How do you display the current time?

2 How do you do the following tasks?

A Create an ArrayList for storing double values?

B Append an object to a List?

C Insert an object at the beginning of a List?

D Find the number of objects in a List?

E Remove a given object from a List?

F Remove the last object from a List?

G Check whether a given object is in a List?

H Retrieve an object at a specified index from a List?

3 Identify the errors in the following code fragment:

1: ArrayList<String> list = new ArrayList<String>();

2: list.add( “Denver” );

3: list.add( “Austin” );

4: list.add( new java.util.Date() );

5: String city = list.get( 0 );

6: list.set( 3, “Dallas” );

7: System.out.println( list.get(3) );

4 Suppose the ArrayList list contains duplicate elements. Does the following code correctly remove all elements from list? If not, correct the code.

1: for ( int i = 0; i < list.size(); i++ )

2: list.remove( element );

5 Explain why the following code fragment displays [1, 3] rather than [2, 3].

1: ArrayList<Integer> list = new ArrayList<Integer>();

2: list.add(1);

3: list.add(2);

4: list.add(3);

5: list.remove(1);

6: System.out.println( list );

6 How do you create an object of the java.util.Calendar class, that represents the current moment in time?

7 For a Calendar object c, how do you get its year, month, date, hour, minute, and second?

8 Using the java.time API, how can you add one month to a LocalDate object? How can you create a LocalDate object that represents the last Friday of the current month?

Get 20% Discount on This Paper
Pages (550 words)
Approximate price: -

Try it now!

Get 20% Discount on This Paper

We'll send you the first draft for approval by at
Total price:

How it works?

Follow these simple steps to get your paper done

Place your order

Fill in the order form and provide all details of your assignment.

Proceed with the payment

Choose the payment system that suits you most.

Receive the final file

Once your paper is ready, we will email it to you.

Our Services

Paper Helper has assembled a team of highly skilled writers with diverse experience in the online writing circles. Our aim is to become a one stop shop for all your Academic/ online writing. Check out below our amazing service!


Essay Writing Services

At Paper Helper, we prioritize on all aspects that creates a good grade such as impeccable grammar, proper structure, zero-plagiarism, and conformance to guidelines. The principal purpose of essay writing is to present the author's evaluation concerning a singular subject about which they have made. Since Professionalism is the mother of every success, try our team of experienced writers in helping you complete your essays and other assignments.


Admission Papers

You have been trying to join that prestigious institution you long yearned for, but the hurdle of an admission essay has become a stumbling block. We have your back, with our proven team that has gained invaluable experience over time, your chance of joining that institution is now! Just let us work on that essay.How do you write an admission essay? How do you begin the essay? For answers, try Quality Custom Writers Now!


Editing and Proofreading

Regardless of whether you're pleased with your composing abilities, it's never an impractical notion to have a second eye go through your work. The best editing services leaves no mistake untouched. We recognize the stuff needed to polish up a writing; as a component of our editing and proofreading, we'll change and refine your write up to guarantee it's amazing, and blunder free. Our group of expert editors will examine your work, giving an impeccable touch of English while ensuring your punctuation and sentence structures are top-notch.


Technical papers

We pride ourselves in having a team of clinical writers. The stringent and rigorous vetting process ensures that only the best persons for job. We hire qualified PhD and MA writers only. We equally offer our team of writers bonuses and incentives to motivate their working spirit in terms of delivering original, unique, and informative content. They are our resources drawn from diverse fields. Therefore your technical paper is in the right hands. Every paper is assessed and only the writers with the technical know-how in that field get to work on it.


College Essay Writing

If all along you have been looking for a trustworthy college essay service provider that provides superb academic papers at reasonable prices, then be glad that you search has ended with us. We are your best choice! Get high-quality college essay writing from our magnificent team of knowledgeable and dedicated writers right now!


Quality Assignment/Homework Help

We give the students premium quality assignments, without alarming them with plagiarism and referencing issues. We ensure that the assignments stick to the rules given by the tutors. We are specific about the deadlines you give us. We assure you that you will get your papers well in advance, knowing that you will review and return it if there are any changes, which should be incorporated.

togel macau togel terbesar bocoran admin jarwo data macau