Java Class Design

Question 1

What does the phrase covariant return types describe?

Answer 1

An overriding method can return a subtype of the return type of the overridden method.

Question 2

Which type determines the version of overridden method to execute using polymoprhism?

Answer 2

Object type

Question 3

When overloading methods, what is the order of priority for matching argument data types?

Answer 3

1. Explicit type
2. Widening primitive conversion
3. Widening reference conversion
4. Boxing conversion
5. Unboxing conversion

Question 4

When overloading methods, if all overloaded methods fail to match, which parameters are considered next?

Answer 4

vargs

Question 5

Which the method of the Object class is invoked when placing objects in a Hashtable?

Answer 5

hashCode

Question 6

Which two things can be referenced from a standard import statement?

Answer 6

Packages and types

Question 7

What is the visibility of a local variable?

Answer 7

Only within the code block that contains its declaration

Question 8

Which three access modifiers are allowed for inner classes?

Answer 8

public, private, protected

Question 9

Which access modifier is allowed when overriding a method with the access modifier public?

Answer 9

public

Question 10

Which primitive-to-reference conversion is not supported when using covariant return types?

Answer 10

Autoboxing

Question 11

Which keyword is used in a subclass constructor to explicitly invoke a superclass constructor?

Answer 11

super

Question 12

Which exception is thrown if a specified type is not a subtype of the object type in a casting operation?

Answer 12

ClassCastException

Question 13

Which method of the Object class compares references rather than their underlying field values?

Answer 13

equals

Question 14

Which the method of the Object class is invoked for the toString method?

Answer 14

hashCode

Question 15

Where is a package statement required to be in a source code file?

Answer 15

The first executable line

Question 16

Which access modifier prevents a method from being overridden in a subclass?

Answer 16

final

Question 17

What is the only access modifier allowed for a top-level class?

Answer 17

public

Question 18

What is the visibility of an anonymous class?

Answer 18

Only within its own class declaration

Question 19

Which access modifiers are allowed when overriding a method with the access modifier protected?

Answer 19

Same or less restricting.

protected, public

Question 20

Which types can access a field or method declared with the access modifier protected?

Answer 20

Subclasses or classes in same package

Question 21

When overloading methods, if there is not an overloaded match after boxing conversion, then which conversion occurs next?

Answer 21

Unboxing conversion

Widening is the answer from Kaplan

Question 22

Which operator tests whether a type is an instance of a specified class using the inheritance hierarchy?

Answer 22

instanceof

Question 23

Which three access modifiers are allowed for class and instance members?

Answer 23

public, private, protected

Question 24

Which type determines the version of a hidden member to use without polymoprhism?

Answer 24

Reference Type

Question 25

When overloading methods, if there is not an overloaded match after unboxing conversion, then which conversion occurs next?

Answer 25

No clear..

Widening is the answer from Kaplan

Question 26

Which the method of the Object class determines the bucket in which an object is placed in a Hashtable?

Answer 26

hashCode

Question 27

Which superclass constructor is implicitly invoked by the compiler in a subclass that does not explicitly invoke a specific superclass constructor?

Answer 27

Constructor with no arguments.

Question 28

What are the three class modifiers that can be used with an outer class?

Answer 28

public, abstract, final

Question 29

Can a constructor have both super and this in the body?

Answer 29

No, calls to super() or this() should be the first statement in a constructor, hence both the calls cannot be there in a constructor.