Java

Question 1

What keyword would be used to refer to the current class instance variable, in order to resolve ambiguity between instance variables & parameters?

Answer 1

this

Question 2

Why might the this keyword be used to invoke the current class constructor?

Answer 2

To reuse the constructor i.e. for constructor chaining

Question 3

The new operator is followed by a call to a ____, which initializes a new object.

Answer 3

Class constructor

Question 4

The super keyword can be used to refer to a parent class instance variable if what is true?

Answer 4

The parent class and child class have the same fields

Question 5

When should the super keyword be used to invoke a parent class method?

Answer 5

If the child class contains the same method as the parent class i.e if the method is being overwritten

Question 6

What four things can the static keyword be applied with?

Answer 6

Variables, methods, blocks, nested classes

Question 7

Where can the final keyword be initialized?

Answer 7

In the constructor

Question 8

What string handling method returns a character at a specified index?

Answer 8

char charAt(int index)

Question 8

What string handling method compares the current string to another object?

Answer 8

int compareTo(Object o)

Question 8

What string handling method concatenates the specified string to the end of the current string?

Answer 8

String concat(String str)

Question 9

What string handling method compares the current string to the specified object?

Answer 9

boolean equals(Object anObject)

Question 10

What string handling method compares the current string to another string while ignoring case considerations?

Answer 10

boolean equalsIgnoreCase(String anotherString)

Question 11

What in Java is a group of similar types of classes & interfaces?

Answer 11

Package

Question 12

What are the three advantages of packages?

Answer 12

Categorizing classes & interfaces; providing access protection; removing naming collision

Question 13

What are the three ways to access a package from other packages?

Answer 13

import package.*; import package.classname; using the fully qualified name.

Question 14

If the import package.* syntax is used, then which of the following three will not be accessible? Classes, interfaces, subpackages

Answer 14

Subpackages

Question 15

If the import package.classname syntax is used, what is the only part of the package that will be accessible?

Answer 15

Declared class

Question 16

When is the fully qualified name of a package generally used?

Answer 16

Two packages have the same class name / To prevent class name collision

Question 17

What is the ordering sequence of a Java program?

Answer 17

Package > import > class

Question 18

What is a reference type in Java that is similar to class and is a collection of abstract methods?

Answer 18

Interface

Question 19

Besides abstract methods, what 3 or 4 things may an interface also contain?

Answer 19

Constants, default or static methods, nested types

Question 20

All the methods of an interface implemented by a class need to be defined in the class, unless what is true?

Answer 20

The class is abstract

Question 21

Can an interface contain any number of methods?

Answer 21

Yes

Question 22

Can you instantiate an interface?

Answer 22

No

Question 23

What is the name of the .java file that an interface is written in?

Answer 23

The same as the name of the interface

Question 24

Can an interface contain constructors?

Answer 24

No

Question 25

Where does the byte code of an interface appear?

Answer 25

In a .class file

Question 26

What is the name of the directory structure containing the bytecode file of an interface?

Answer 26

The same as the name of its package

Question 27

What must all fields in an interface be declared as?

Answer 27

Static and final

Question 28

Can an interface be extended by a class?

Answer 28

No

Question 29

Can an interface extend multiple interfaces?

Answer 29

Yes

Question 30

Are methods in an interface implicitly public?

Answer 30

Yes

Question 31

What must a class do if it does not perform all the behaviors of an implemented interface?

Answer 31

Declare itself as abstract

Question 32

Can a class implement more than one interface at a time?

Answer 32

Yes

Question 33

Can a class extend more than one class?

Answer 33

No

Question 34

What are events that occur during the execution of programs that disrupt the normal flow of instructions?

Answer 34

Exceptions

Question 35

What is an exception in Java?

Answer 35

An object that wraps an occurred error event within a method

Question 36

What three things does an exception contain?

Answer 36

Info about the error including its type; the state of the program when the error occurred; possibly other custom information

Question 37

What are the three categories of exceptions?

Answer 37

Checked, unchecked, errors

Question 38

What type of exception is one which the compiler forces you to handle explicitly?

Answer 38

Checked

Question 39

What type of exception is generated by a method that must declare it that throws it?

Answer 39

Checked

Question 40

What type of exceptions are errors and RuntimeExceptions?

Answer 40

Unchecked

Question 41

What type of exception is one upon which it is assumed that the application cannot do anything to recover from it?

Answer 41

Unchecked

Question 42

What keywords are used together by a method to catch exceptions?

Answer 42

try, catch

Question 43

What keyword is used by a method to declare a checked exception it does not handle?

Answer 43

throws

Question 44

What keyword is used to postpone the handling of an unchecked exception?

Answer 44

throws

Question 45

What keyword is used to invoke an exception explicitly?

Answer 45

throw

Question 46

What code block keyword is used to run any cleanup-type statements that the programmer wants to excecute, regardless of any exceptions occurring in the preceding try & catch blocks?

Answer 46

finally

Question 47

What is used in Java to solve the problem of fixed size limits of arrays?

Answer 47

Collection framework

Question 48

What three things do all collection frameworks contain?

Answer 48

Interfaces, implementations (classes), algorithms.

Question 49

What interface extends Collection and declares the behavior of a collection that stores a sequence of events?

Answer 49

List

Question 50

What exception will some list methods throw if the collection cannot be modified?

Answer 50

UnsupportedOperationException

Question 51

What exception will some list methods throw when one object is incompatible with another?

Answer 51

ClassCastException

Question 52

What part of collection framework provides dynamic arrays in Java?

Answer 52

ArrayList

Question 53

What class does ArrayList inherit?

Answer 53

AbstractList

Question 54

What interface is a Collection that cannot contain duplicate elements?

Answer 54

Set

Question 55

What does the Map interface do?

Answer 55

Maps unique keys to values so they can be retrieved later