Week 2 - Java foundations - Classes, Objects, Flow Control, Arrays

Question 1

What is the purpose of the package declaration in a Java file?

Answer 1

The package declaration declares the package in which the class will reside. Packages are a way of organizing classes, interfaces, and enums in a hierarchical manner.

Question 2

What is the naming convention for Java packages?

Answer 2

Packages follow a naming convention of lowercase characters separated by periods in the reverse way you would specify a web domain - thus, com.revature.mypackage instead of mypackage.revature.com.

Question 3

What is a fully qualified class name in Java?

Answer 3

A fully qualified class name is the package declaration followed by the class name, in order to uniquely identify the class.

Let’s say we have a Java class named “Employee” that is located in the “com.company.hr” package. The fully qualified class name for this class would be “com.company.hr.Employee”.

Question 4

What is the purpose of an import statement in Java?

Answer 4

An import statement is used to pull in other classes so that the programmer can just use the class name without the package.

Question 5

What is the default package imported in Java?

Answer 5

By default, everything in the java.lang package is imported in Java, which gives us the System class.

Question 6

What is a class declaration in Java?

Answer 6

A class declaration in Java declares a class with a specific name, and it is defined by wrapping it with curly braces.

Question 7

What is the name of the method that serves as the entry point for Java applications?

Answer 7

The main method serves as the entry point for Java applications

Question 8

What is the purpose of the main method in Java?

Answer 8

The main method is a special method that specifies the entry point of the application. It is invoked by the JVM when the code is executed.

Question 9

What type of data does the main method return in Java?

Answer 9

The main method does not return any data in Java. The void keyword is used to denote this.

Question 10

What is the purpose of the array of String objects passed to the main method in Java?

Answer 10

The array of Strings defined in the main method parameters are passed from the command line when the java command is run. They are used to pass input to the program at runtime.

Question 11

What are the different scopes of a variable in Java?

Answer 11

The different scopes of a variable in Java are: instance, class, method, and block.

Question 12

What is instance scope in Java?

Answer 12

Instance scope means that the variable is attached to individual objects created from the class. When an instance-scoped variable is modified, it has no effect on other, distinct objects of the same class.

Question 13

What is class scope in Java?

Answer 13

Class scope means that the variable resides on the class definition itself. When objects update a class-scoped variable, the change is reflected across all instances of the class. Class scope is declared with the static keyword.

Question 14

What is the method scope in Java?

Answer 14

Method scope is the scope of a variable declared within a method block, whether static or instance. Method-scoped variables are only available within the method they are declared and do not exist after the method finishes execution.

Question 15

What is block scope in Java?

Answer 15

Block scoped variables only exist within the specific control flow block, of which there are several in Java: for, while, and do-while loops, if/else-if/else blocks, switch cases, or even just regular blocks of code declared via curly braces ({}).

Question 16

What is the difference between a class and an object in Java?

Answer 16

A class is a template used to instantiate objects. An object is an instance of a class in memory.

Question 17

What is a reference variable in Java?

Answer 17

A reference variable is a variable that stores the reference to an object in memory. It is used to interact with objects through their reference, which is the memory address used by the JVM to find a particular

Question 18

Which is not a rule for which you can create a custom class in Java?

Answer 18

Syntax rules

Question 19

What is TDD?

Answer 19

Test-driven development, or TDD, is a software development process that involves writing unit tests before implementing application code.

Question 20

What is the TDD process?

Answer 20

The TDD process involves designing the interface/function, writing tests that use that function, refactoring method signatures, implementing functions, and running tests to verify functionality.

Question 21

What is unit testing?

Answer 21

Unit testing is the testing of individual software components in isolation from the rest of the system, accomplished by writing tests that execute the code we want to inspect.

Question 22

Why is TDD useful in software development?

Answer 22

Following the TDD process ensures that a valid unit test exists for any class or method written, and gives developers confidence in refactoring code without breaking existing functionality. When issues arise, the pinpointing of problems is easier with TDD.

Question 23

What is the most common unit testing framework in Java?

Answer 23

JUnit is the most common unit testing framework in Java.

Question 24

When following the Test Driven Development process (TDD), when should the tests be written?

Answer 24

Before any code is written

Question 25

What is the testing of individual software components in isolation from the rest of the system?

Answer 25

Unit testing

Question 26

A unit test should be run…?

Answer 26

Until the test passes

Question 27

According to TDD, code should be rewritten…?

Answer 27

When a test case fails

Question 28

What are the benefits of using TDD in software development?

Answer 28

Benefits of using TDD include catching bugs early in the development process, ensuring that all code is tested for functionality, providing confidence in the codebase, and making debugging easier.

Question 29

Why is TDD important in software development?

Answer 29

TDD is important in software development because it ensures that most if not all code being written is tested for functionality. This can help catch bugs early on in the development process, leading to more reliable and robust code.

Question 30

JUnit Testing Approaches
In both the approaches the workflow remains common:

Answer 30

Creating a test case
Reviewing it
Rework if corrections needed
Execute the test case
Analyze the test results

Question 31

Automated Testing is preferred over manual Testing for the following reasons:

Answer 31

Manual testing requires a great deal of human effort.
Manual testing also requires more resources to be allocated.
Schedule constraints may put time allocated for testing at a premium.

Question 32

What Is JUnit?

Answer 32

JUnit is an open-source framework that is used for writing and executing unit tests in Java programming language. It is one of the best-known unit testing frameworks.

Question 33

Some crucial reasons for unit testing are listed below:

Answer 33

Unit testing helps testers and developers understand the root causes of errors.
Unit testing helps with documentation.
Unit testing fixes defects early in the development phase.
Unit testing helps with code reusability.

Question 34

Generally, the software goes through four levels of testing:

Answer 34

Unit Testing, Integration Testing, System Testing, and Acceptance Testing.

Question 35

In JUnit, what verifies that the state of the application meets what is expected?

Answer 35

Assertions

Question 36

In JUnit, what annotation declares a method as a test method?

Answer 36

@Test

Question 37

In JUnit, what annotation declares a setup method that runs once, before all other methods in the class?

Answer 37

@BeforeClass

Question 38

In JUnit, what annotation declares a setup method that runs before each test method?

Answer 38

@Before

Question 39

In JUnit, what annotation declares a tear-down method that runs before each test method?

Answer 39

@After

Question 40

A constructor declares how an object is to be instantiated and initialized from the class “blueprint”.

Answer 40

A constructor is a special method that initializes objects of a class.

It specifies how an object should be created and what initial values should be assigned to its attributes.

Question 41

A constructor is declared like a method, except

Answer 41

its method signature does not contain a return type, and a constructor always has the same name as the class

Question 42

The new object created by the constructor is always of the ________

Answer 42

class in which the constructor is declared.

Question 43

‘this’ refers to the object which is being instantiated. What are two ways to use this

Answer 43

it is used to initialize instance variables
to call other constructors (this is called constructor chaining)

Question 44

What does the ‘super’ keyword do?

Answer 44

references the “super”, or parent, class.

Question 45

When invoked as a method (super()), calls ______

Answer 45

the parent class constructor will be called

Question 46

A super() call (or a this() call) must ______

Answer 46

be the first line of any constructor

Question 47

The “default” constructor takes no arguments and simply calls super() (see above) - sometimes it is referred to as the ______

Answer 47

“default, no-args” constructor

Question 48

The if statement lets us execute a statement or a block of statements only if

Answer 48

some conditional test turns out to be true.

Question 49

The if statement depends on the use of

Answer 49

Boolean expressions.

Question 50

A Boolean expression is an expression that returns a

Answer 50

simple true or false result.

Question 51

A statement or block of statements is executed should the result of the Boolean expression be true
else and else if statements provide alternate routes for program execution to

Answer 51

follow should the result of the Boolean expression be false.

Question 52

switch statements attempt to

Answer 52

match some variable with the value it contains

Question 53

The following are the Java keywords used to create a variety of loops, depending on the looping situation required:
for : ____
while : ____
do-while : ____

Answer 53

for : This type of loop is used to execute a block of code a specific amount of times.
while : This type of loop evaluates a Boolean expression before executing the block of statements. Therefore, it may never execute.
do-while : This type of loop executes the block of statements one time then evaluates the Boolean expression at the end. Therefore, this type of loop executes at least once.

Question 54

The Java keyword break can be used to:

Answer 54

Exit a loop
Implement a “goto” flow control that exists in other programming languages
Terminate a switch statement sequence

Question 55

The Java keyword continue is used to

Answer 55

skip the current iteration of a loop.

Question 56

A break statement…

Answer 56

Can be used either with or without a label

Question 57

The main difference between a break and a continue statement is…

Answer 57

A continue directs program flow to the next loop iteration, a break immediately directs program flow out of the loop

Question 58

A continue statement Can be used either with or without a label
T/F?

Answer 58

True

Question 59

Which type of loop is most appropriate for executing a specific number of times?

Answer 59

for loop

Question 60

Which type of loop may not execute its code at all?

Answer 60

while loop

Question 61

Which type of loop will run its code at least once?

Answer 61

do-while loop

Question 62

Which type of loop will run its code at least once?

Answer 62

do-while loop

Question 63

Loops rely on what type of expression to tell it to stop looping?

Answer 63

Conditional

Question 64

Define an array.

Answer 64

An array is a contiguous block of memory storing a group of sequentially stored elements of the same type. Arrays in Java are of a fixed size and cannot be resized after declaration.

Question 65

What is an element

Answer 65

Each item of an array

Question 66

All elements of an array must be of the same

Answer 66

type

Question 67

3 ways to declare an array.

Answer 67

int[] arr;
int[] arr = {1, 2, 3, 4, 5};
int[] arr = new int[5];