Concepts

Question 1

Bytecode

Answer 1

An intermediate code between the source code and machine code.

Question 2

JVM

Answer 2

Java Virtual Machine. It interprets the bytecode into machine code. It is part of the JRE.

Question 3

JDK

Answer 3

Java Development Kit. It includes JRE, a Java compiler, a debugger, and more;

Question 4

JRE

Answer 4

Java Runtime Environment; Executes Java programs; It includes JVM and Java libraries.

Question 5

Declaring a variable

Answer 5

what kind of data it will store

Question 6

What is a Java class?

Answer 6

a template (blueprint) that is used to create objects. It consists of data members and methods.

Question 7

Object

Answer 7

objects have states and behaviors.

Question 8

Eclipse

Answer 8

a Java IDE (Integrated Development Environment). It includes text editor, compiler or interpreter, and debugger, like IntelliJ IDEA

Question 9

IDE

Answer 9

Integrated Development Environment. for example, visual studio.

Question 10

How to create a Java object?

Answer 10

Declaration; Instantiation; Initialization

ClassName object = new ClassName()

Question 11

What are Java constructors?

Answer 11

• A special method that is used to initialize objects
• You would call a constructor when an object is created. It can be used to set initial values for object attributes.
• Note that the constructor name must match the class name and it can’t have a return type (like void)

Question 12

Pascal case

Answer 12

a naming convention in which the first letter of each word in a compound word is capitalized.

Question 13

SDK

Answer 13

software development kit

Question 14

Java variable

Answer 14

a location in memory (storage area) to hold data. Each variable should be given a unique name (identifier)

Question 15

statically-typed language

Answer 15

It means that all variables must be declared before they can be used.

Question 16

Java expressions

Answer 16

a construct made up of variables, operators, literals, and method calls.

Question 17

Java operators

Answer 17

• arithmetic
• assignment
• comparison
• logical

Question 18

truth table

Answer 18

a mathematical table used to determine if a compound statement is true or false.

component statement

Question 19

public in Java

Answer 19

an access modifier

• the class is accessible by any other class
• the code is accessible for all classes

Question 20

default in Java

Answer 20

an access modifier

• the class is only accessible by classes in the same package.
• the code is only accessible in the same package.

Question 21

private in Java

Answer 21

an access modifier

- the code is only accessible within the declared class.

Question 22

final in Java

Answer 22

if you don’t want the ability to override existing attributes values, declare attributes as final

Question 23

static methods/attributes in Java

Answer 23

can be accessed without creating an object of the class first

Question 24

Java statement

Answer 24

a complete unit of execution

Question 25

Refactor Code

Answer 25

changing the structure of a program without changing what it does

Question 26

Side Effect

Answer 26

anything a method does besides computing and returning a value

• any change of instance or class field values
• drawing something on the screen
• writing to a file
• a network connection

Question 27

Call Site (Method Invocation)

Answer 27

the point of code when the method is called

Question 28

Operator Precedence

Answer 28

rules that define the order that expressions are evaluated

Question 29

indexOf() Method

Answer 29

if indexOf doesn’t find the string we’re searching for, it returns -1

Question 30

string.charAt() Method

Question 31

Method Overloading

Answer 31

allows you to have multiple methods using the same method name

Question 32

Value Type

Answer 32

• store values

- value types are copied by value

Question 33

Reference Type

Answer 33

• store reference

- reference types are copied by reference. We have two references pointing to the same object in the memory.

Question 34

String Literal Pool

Answer 34

a storage area in Java heap where string literals stored.

Question 35

Literal

Answer 35

Any constant value which can be assigned to the variable

Question 36

string1 == string2 vs. string1.equals(string2)

Answer 36

== will test that the variables are referring to the same object, not that they refer to the objects with the same value
== checks the reference equality not the contents
.equals method checks for value equality

Question 37

StringBuilder Class

Answer 37

allows modifying the strings without creating new string objects

Question 38

Garbage Collection

Answer 38

to free heap memory by destroying unreachable objects.

Question 39

Stack vs Heap

Answer 39

The major difference between Stack memory and heap memory is that the stack is used to store the order of method execution and local variables while the heap memory stores the objects and it uses dynamic memory allocation and deallocation.

Question 40

Mutable Reference Type

Answer 40

a reference to an object that can be changed

Question 41

return a reference vs. return an object

Answer 41

method chaining for the method that returns an object

Question 42

single quotes vs. double quotes

Answer 42

Use single quotes for literal chars and double quotes for literal Strings