Question 1

Unfortunately, polymorphic programs make it difficult to add new capabilities to a system.

Accepted Answer

false

Question 2

Say that the situation is the same as in question 7. Which of the following array declarations is correct for an array that is expected to hold up to 10 objects of types Rat, Mouse, and PocketMouse?

Accepted Answer

Rodent[] array = new Rodent[10];

Question 3

All methods in a final class must be explicitly declared final.

Accepted Answer

false

Question 4

Polymorphism enables objects of different classes that are related by a class hierarchy to be processed generically

Accepted Answer

true

Question 5

If same message is passed to objects of several different classes and all of those can respond in a different way, what is this feature called?

Accepted Answer

polymorphism

Question 6

Using higher degree of abstraction __________

Accepted Answer

can be safer

Question 7

In terms of stream and files ____________

Accepted Answer

Abstraction is called a stream and device is called a file

Question 8

Which of the following classes fail to compile?

abstract class X { abstract void method(); }

abstract class Y extends X { }

class Z extends Y { void method() { System.out.println("Class Z"); } }

Accepted Answer

All classes compile

Question 9

What is polymorphism in Java?

Accepted Answer

It is when a single variable is used with several different types of related objects at different places in a program.

Question 10

There can be a try block without catch block but vice versa is not possible.

Accepted Answer

true

Question 11

A method must do either of two things with a checked exception. What are those two things?

Accepted Answer

(1) Handle the exception in a catch{} block, or (2) throw the exception to the method that called this method.

Question 12

Which are the two blocks that are used to check error and handle the error?

Accepted Answer

Try and catch

Question 13

Casting superclass references to subclass references is known as downcasting.

Accepted Answer

true?

Question 14

Polymorphism is a feature of object oriented programming.

Accepted Answer

true

Question 15

If a subclass reference is assigned to a superclass variable, the variable must be cast back to the subclass before any subclass methods can be called with it.

Accepted Answer

true?

Question 16

Which problem may arise if we use abstract class functions for polymorphism?

Accepted Answer

All the derived classes must implement the undefined functions?

Question 17

The major drawback to polymorphically designed programs is that they do not take into account the future addition or deletion of classes

Accepted Answer

false

Question 18

Which of the following classes fail to compile? class X { } abstract class Y { } abstract class Z { abstract void method(); }

Accepted Answer

All classes compile?

Question 19

What is an advantage of polymorphism? Group of answer choices

Accepted Answer

The same program logic can be used with objects of several related types.

Question 20

Which among the following is not a level of abstraction?

Accepted Answer

View level?

Question 21

Higher the level of abstraction, higher are the details.

Accepted Answer

False?

Question 22

Which class is used to handle the input and output exceptions?

Accepted Answer

IOExceptions

Question 23

Which of the following ways can be used to handle exceptions? X: By wrapping the desired code in a try block followed by a catch block to catch the exceptions. Y: List the desired exceptions in the throws clause of the method and let the caller shit

Accepted Answer

Both X and Y

Question 24

An exception may arise when _______________

Accepted Answer

Input given is invalid?

Question 25

If the Java program is using assertions, it must be run with -ea or -enableassertions switches.

Accepted Answer

False

Question 26

Encapsulation is supported by ___________

Accepted Answer

Classes?

Question 27

Which among the following is the language which supports classes but not polymorphism?

Accepted Answer

Ada

Question 28

Which among the following is not true for polymorphism?

Accepted Answer

Increases overhead of function definition always?

Question 29

Objects of abstract superclasses can be instantiated.

Accepted Answer

false

Question 30

What is an abstract method?

Accepted Answer

An abstract method is one without a body that is declared with? the reserved word abstract.

Question 31

Which of the following is FALSE about abstract classes in Java

Accepted Answer

A class can inherit from multiple abstract classes.?

Question 32

Can an abstract parent class have non-abstract children?

Accepted Answer

Yes--an abstract parent can have both abstract and non-abstract children.?

Question 33

Which of the following classes fail to compile?

abstract class X { abstract void method(); }

abstract class Y extends X { }

class Z extends Y { void method() { System.out.println("Class Z"); } }

Accepted Answer

All classes compile

Question 34

Abstraction can apply to ____________

Accepted Answer

Control and data

Question 35

To catch the exceptions ___________________

Accepted Answer

An object must be created to catch the exception

Question 36

You are writing a program to check people into a hotel. People over 65 get a 10% discount. How would you write the program?

Accepted Answer

Normal if-else programming logic will be used.?

Question 37

How many catch blocks can a single try block can have?

Accepted Answer

As many as required

Question 38

Say that a method catches an IOException in a catch{} block. Is it possible for that block to do some processing and then throw the same exception to the caller?

Accepted Answer

Yes---as long as the method also has a throws clause for that exception.

Question 39

Program throws ___________ if assert statement fails.

Accepted Answer

java.lang.AssertionError

Question 40

Which among the following best describes polymorphism?

Accepted Answer

It is the ability for a message/data to be processed in more than one form

Question 41

Examine the following code: String str = "Hot Java"; boolean switch = str instanceof String; What value is placed in switch?

Accepted Answer

true ?

The instanceof operator checks whether an object is an instance of a specific class.

str is a String object, so str instanceof String evaluates to true.

Question 42

Here is a method definition: int compute( a int, y double ){ . . . .} Which of the following has a different signature?

Accepted Answer

int compute( a int, y int ){ . . . .}?

yung signature ang tinitignan is name and parameter list type and order

Question 43

Here is an abstract method defined in the parent: public abstract int sumUp ( int[] arr ); Which of the following is required in a non-abstract child?

Accepted Answer

public int sumUp ( long[] arr ) { . . . }?

Question 44

If 2 classes derive one base class and redefine a function of base class, also overload some operators inside class body. Among these two things of function and operator overloading, where is polymorphism used?

Accepted Answer

Operator overloading only?

Question 45

If two classes combine some private data members and provides public member functions to access and manipulate those data members. Where is abstraction used?

Accepted Answer

Using public member functions to access and manipulate the data members

Question 46

Which of the following classes fail to compile?

abstract class X { abstract void method(); }

abstract class Y extends X { }

class Z extends Y { void Method() { System.out.println("Class Z"); } }

Accepted Answer

Z?

Question 47

Which of the following classes fail to compile?

abstract class X { abstract void method(); }

abstract class Y extends X { void Method() { } }

class Z extends X { void method() { } }

Accepted Answer

All classes compile?

Question 48

Which is the universal exception handler class?

Accepted Answer

Exceptions?

Question 49

What are two exception classes in hierarchy of java exceptions class?

Accepted Answer

Runtime exceptions and other exceptions?

Question 50

Polymorphism is possible in JAVA language.

Accepted Answer

True?

Question 51

class X { } abstract class Y { } class Z { abstract void method(); }

Accepted Answer

Z?

Question 52

Can an abstract class define both abstract methods and non-abstract methods?

Accepted Answer

Yes--the child classes inherit both.

Question 53

Which among the following can be viewed as combination of abstraction of data and code.

Accepted Answer

Class?

Question 54

Which of these is a super class of all errors and exceptions in the Java language?

Accepted Answer

Throwable?

Question 55

Which among the following is not a method of Throwable class?

Accepted Answer

public Char toString()?

Question 56

Say that methodA calls methodB, and methodB calls methodC. MethodC might throw a NumberFormatException. Can the program be written so that methodA handles the exception?

Accepted Answer

Yes, if the headers for methodC and methodB say ...throws NumberFormatException?

Question 57

Which of the following statements is true?

Accepted Answer

It is sometimes good practice to throw an AssertionError explicitly.?

Question 58

Which of the following statements is true?

Accepted Answer

It is sometimes good practice to throw an AssertionError explicitly.?

Question 59

Which one is runtime polymorphism?

Accepted Answer

option2: MethodOverriding?

Question 60

What is the name of the class that is the ancestor to every other class in Java?

Accepted Answer

object?

Question 61

If a class leaves one method in an interface undeclared, the class is implicitly declared by Java as an abstract class.

Accepted Answer

true?

Question 62

The ability to define more than one function with the same name is called?

Accepted Answer

Polymorphism

Question 63

class X { abstract void method(); } abstract class Y extends X { } class Z extends Y { void method() { } }

Accepted Answer

x?

Question 64

Which of the following is correct?
Group of answer choices

All classes of Exception extend from Throwable.

All classes of Error extend from Exception.

All classes of Exception extend from Error.

All classes of Throwable extend from Exception

Accepted Answer

All classes of Exception extend from Throwable.?

OOPf4

formative of hell

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