Questions regarding java

Question 1

If A "Is-A" B, what else can we say about the relationship between class A and class B?

Class A extends class B

Class A inherits from class B

Class A derives from class B.

None of the above.

All of the above.

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Question 2

What tool is used to show inheritance or composition relationships among classes.

a class diagram

a flow chart

an object diagram

a family tree

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Question 3

Which of the following is a specialized version of a class.

an ancestor

a subclass

a superclass

class Object

class Class

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Question 4

Which of the following statements is true?

Objects NEVER change the class to which they belong.

In some situations, a variable may be bound to DIFFERENT types of objects.

The behavior of any object is determined by the OBJECT'S CLASS and not by the data type of the variable that references it.

All of the above.

None of the above.

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Question 5

Given this start to a class definition: public class Beta extends Alpha { ... } What is true about instance variables from Alpha?

Class Beta must redeclare all of Alpha's instance variables.

They should not be redeclared in Beta.

The Beta class should redeclare only those instance variables from Alpha that it wants.

Class Beta should redeclare only the private instance variables from Alpha.

None of the above

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Question 6

If class Fruit is the superclass of class Apple, which of the following is also true?

Fruit is the base class of Apple

Fruit is the parent class of Apple

Apple "Is-A" Fruit

All of the above

None of the above

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Question 7

If a class definition does not include the keyword extends, which of the following is true?

The class has no sub class

The class has no super class

The class implicitly derives from Class.

The class implicitly derives from Object.

None of the above

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Question 8

Which of the following things would prevent a method declaration in a subclass from properly overriding an inherited method?

not matching the method name

not matching the return type

not matching the parameter "signature" (number, order and data types of parameters)

trying to make a public method private

All of the above

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Question 9

What is always the very first thing that occurs in the constructor of a derived class?

instance variables are initialized

the value true is returned

a call to the superclass constructor is made

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Question 10

Which of the following statements creates a composition (or aggregation) relationship?

public class Fun extends Hun { ... }

return new Fun();

if ( myThing instanceof Point ) { ... }

private Widget myThing;

Boo Hoo

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Question 11

Which Java keyword can be used to access the super class version of an overridden method from within the sub class?

override

super

new

this

extends

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Question 12

Given the following code (assume that the statements compile with NO syntax errors):

Red hot = new Red(); Green top = hot; Orange ocean = new Blue(); hot = ocean;

What is the static type of 'top'?

Green

hot

Red

top

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Question 13

Given the following code (assume that the statements compile with NO syntax errors):

Red hot = new Red(); Green top = hot; Orange ocean = new Blue(); hot = ocean;

What is the dynamic type of 'ocean' after all the statements have been executed? (Tip: draw an object diagram!)

Orange

hot

Red

Blue

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Question 14

Given the following code (assume that the statements compile with NO syntax errors):

Red hot = new Red(); Green top = hot; Orange ocean = new Blue(); hot = ocean;

What is the dynamic type of 'hot' after all the statements have been executed? (Tip: draw an object diagram!)

Red

ocean

Blue

Orange

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Question 15

What determines which version of an overridden method is executed?

the static type of the variable that acts as the 'qualifier' in the method call

the dynamic type of the variable that acts as the 'qualifier' in the method call

the data types of the arguments of the method call

the name of the class where the method call is located

the name of the method

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Question 16

What determines which version of an overloaded method is executed?

the static type of the variable that acts as the 'qualifier' in the method call

the dynamic type of the variable that acts as the 'qualifier' in the method call

the data types of the arguments of the method call

the name of the class where the method call is located

the name of the method

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Question 17

A programmer writing code in class Point attempts to override the following inherited method: public boolean equals( Object o ) { ... } but does not match the method signature exactly. Instead, the programmer uses the following method signature: public boolean equals( Point p ) { ... } What is the result?

A syntax error occurs because the method signatures do not match.

The code compiles and works fine -- the method has been successfully overridden.

The code compiles, but the inherited method has not been overridden -- it has been overloaded instead.

The compiler automatically changes the method signature to match the inherited method.

The compiler issues a warning, but the method is successfully overridden.

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Question 18

Given the following class hierarchy: Siamese "Is-A" Feline "Is-A" Mammal "Is-A" LivingThing Which of the following is true?

( new Mammal() ) instanceof LivingThing

( new Feline() ) instanceof LivingThing

( new Siamese() ) instanceof LivingThing

All of the above

None of the above

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Question 19

A type cast using reference type is a promise to the compiler that the dynamic type of the expression will conform to the type specified in the cast. What happens if this promise is broken?

A syntax error will occur.

The dynamic type will be changed to match the type specified in the cast.

A ClassCastException will be thrown.

The JRE will request a replacement type from the user.

The type cast will be ignored.

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Question 20

How many different classes can a sub class derive from, using the keyword extends?

A sub class can extend directly from mutliple super classes.

exactly one class

any number of classes as long as an import statement is used