Week 1 - Programming Foundations - Learn basic programming constructs using Java

Question 1

What is a Full Stack Developer?

Answer 1

Full-stack developers straddle two separate development domains: the front end and the back end.
Those knowledgeable in both front end and back end are called full stack developers, meaning they are well versed in both disciplines.

Question 2

What is a front-end developer?

Answer 2

They work to optimize the visible parts of an application for web browsers and mobile devices.
Front end platforms are usually built with HTML, CSS, and JavaScript; however, they can also be made via pre-packaged code libraries or content management systems like WordPress.

Question 3

What is a back-end developer?

Answer 3

refine the software code that communicates with servers, databases, or other proprietary software that conveys information to front end interfaces

Question 4

What class is used to read from the console

Answer 4

Scanner class

Question 5

what do the following read?
nextBoolean()
nextByte()
nextDouble()
nextFloat()
nextInt()
nextLine()
nextLong()
nextShort()

Answer 5

Reads a boolean value from the user
Reads a byte value from the user
Reads a double value from the user
Reads a float value from the user
Reads a int value from the user
Reads a String value from the user
Reads a long value from the user
Reads a short value from the user

Question 6

Java syntax to input an object and hold the string input?

Answer 6

Scanner sc = new Scanner(System.in);
String name = sc.nextLine();

Question 7

What is the Scanner class used for?

Answer 7

Parsing input from text into primitives and strings, from a File or InputStream

Question 8

Who invented Java?

Answer 8

Java was invented at Sun Microsystems by a team led by James Gosling. It was first released in 1995.

Question 9

Who currently maintains Java?

Answer 9

Java is currently owned and maintained by the Oracle Corporation, which acquired Java when it acquired Sun Microsystems in 2010.

Question 10

Why Java? What are the advantages?

Answer 10

Java is a high-level, compiled, strongly typed object-oriended programming (OOP) language. The advantages of Java are many: it is platform independent, has a C-language inspired syntax, provides automatic memory management, has an extensive built-in runtime library, is supported by the Oracle corporation, and has a rich open source community

Question 11

What is “object-oriented”?

Answer 11

It has the constructs of classes and objects built into the language. It also allows us to use various principles of object-oriented programming.

Question 12

What are classes?

Answer 12

They are the blueprints for how to create objects that contain a certain state - which is represented by fields (variables) - and behavior - which is defined via methods.

Question 13

What are objects?

Answer 13

They are instances of class definitions. Each object has an identity, a behavior, and a state. They are logical entities.

Question 14

Java is not 100% object-oriented because _____

Answer 14

it still has primitive values

Question 15

What are the 8 primitive values?

Answer 15

byte: an 8-bit integer value.
short: a 16-bit integer value.
int: a 32-bit integer value.
long: a 64-bit integer value.
float: a single-precision 32-bit floating point value.
double: a double-precision 64-bit floating point value.
boolean: a true/false value.
char: a 16-bit Unicode character value.

Question 16

Why are primitive values “primitive”?

Answer 16

These types are called “primitive” because they are not objects; they do not have methods or attributes like objects do. Instead, they are simple values that can be assigned, compared, and used in arithmetic operations. Primitive values are stored directly in memory and can be accessed quickly, which makes them more efficient than objects in terms of memory usage and performance.

Question 17

Which two constructs characterize an object-oriented programming language?

Answer 17

Classes and objects.

Question 18

This line declares a method called main

Answer 18

public static void main(String[] args)

Question 19

A method is…?

Answer 19

An executable element inside a class

Question 20

A reference variable is…?

Answer 20

A variable that stores the reference to an object in memory

Question 21

What does compilation mean?

Answer 21

to transform a program written in a high-level programming language from source code into object code.

Question 22

Source code must go through several steps before it becomes an executable program. Explain the two steps.

Answer 22

The first step is to pass the source code through a compiler, which translates the high-level language instructions into object code.

The final step in producing an executable program — after the compiler has produced object code — is to pass the object code through a linker. The linker combines modules and gives real values to all symbolic addresses, thereby producing machine code.

Question 23

Java, being a platform-independent programming language, doesn’t work on the one-step compilation. Instead, it involves a two-step execution

Answer 23

The first step is through an OS-independent compiler
The second, is in a virtual machine (JVM) which is custom-built for every operating system.

Question 24

The ______ translates the high-level language instructions into object code.

Answer 24

compiler

Question 25

The _____ combines modules and gives real values to all symbolic addresses, thereby producing machine code.

Answer 25

linker

Question 26

The Java source code file is passed through the compiler, which then encodes the source code into a machine-independent encoding known as _____

Answer 26

bytecode

Question 27

4. Which of these is NOT a component when executing a Java program in the Java Virtual Machine (JVM)? Why?

Assembler
ClassLoader
Bytecode Verifier
Just-In-Time Compiler

Answer 27

Assembler - Assembler, on the other hand, is a component of the traditional compilation process, in which source code is translated into machine code directly, rather than being compiled to bytecode for execution in the JVM

Question 28

The three components when executing a Java program in the Java virtual machine (jvm)?

Answer 28

ClassLoader is responsible for loading Java classes into memory as they are needed during program execution.

Bytecode Verifier ensures that the bytecode instructions are safe and conform to the Java language specification before they are executed.

Just-In-Time Compiler (JIT) dynamically compiles frequently used bytecode instructions into native machine code, optimizing program performance.

Question 29

What are reference types?

Answer 29

Types are defined by classes in the Java application Programming Interface (API) or by classes you create rather than by the language itself.

Reference types are created using the new keyword, which allocates memory for an object on the heap and returns a reference to it. Reference variables store the reference to the object, rather than the object itself.

Classes: Classes are templates or blueprints that define the attributes and behaviors of objects.

Interfaces: Interfaces are similar to classes, but they only define method signatures without implementations. Classes can implement interfaces to fulfill the contract defined by the interface.

Arrays: Arrays are ordered collections of elements, which can be of any type, including other reference types.

Question 30

What is the difference between a primitive and a reference variable?

Answer 30

A primitive variable stores a value, a reference variable stores the memory address of an object
Memory allocation: Primitive variables are allocated memory on the stack, whereas reference variables are allocated memory on the heap.

Question 31

What is the default type of variable used for decimals?

Answer 31

Double

Question 32

How many bit is a byte?

Answer 32

8 bit

Question 33

How many bit is a short?

Answer 33

16 bit

Question 34

How many bit is a char?

Answer 34

16 bit

Question 35

How many bit is an int?

Answer 35

32 bit

Question 36

How many bit is a long?

Answer 36

64 bit

Question 37

How many bit is a float?

Answer 37

32 bit

Question 38

How many bit is a double?

Answer 38

64 bit

Question 39

Explain what a String is

Answer 39

they are immutable, constant objects derived from the String class. To be immutable means that the state or value of the object cannot be altered once created - this is accomplished by having internal, private and final fields and not implementing any “setter” methods which would alter the state of those fields.

Question 40

When comparing Strings, the == operator will compare ____

Answer 40

Memory addresses

Question 41

What will be printed by the following block of Java code? Why?
String str1 = “my string”;
str1.concat(“ is the best!”);
System.out.println(str1);

Answer 41

“my string” because concat() method of the String class returns a new String object that represents the concatenation of the original String and the argument string. However, the original String object is not modified by the concat() method. Therefore, if the concat() method is called on a String object, like str1 in the code above, a new String object is returned but the original String object remains unchanged.

Question 42

What is debugging?

Answer 42

Debugging in computer programming is a multi-step process that involves identifying a problem, isolating the source of the problem, and then either correcting the problem or determining a way to work around it.

Question 43

In software development, the debugging process begins __________

Answer 43

when a developer locates a code error in a computer program and is able to reproduce it. Debugging is part of the software testing process and is an integral part of the entire software development lifecycle.

Question 44

Repeatedly dividing the code into halves and commenting out one half to find an error is known as the _____ method of debugging.

Answer 44

Binary search

Question 45

Each JVM thread (a path of execution) is associated with a

Answer 45

stack that’s created when the thread is created

Question 46

A new _____ is created each time a method is called.

Answer 46

Frame

Question 47

A _____ is a report of the active stack frames at a certain point in time during a thread’s execution.

Answer 47

stack trace

Question 48

In Java there are three methods to print exception information. All of them are present in the _____ class.

Answer 48

Throwable

Question 49

What is casting?

Answer 49

the process of converting a data type to another data type. This is also called type casting. Casting is necessary is some situations when we receive a data type that needs to have some actions performed on it that its original form cannot handle.

Question 50

Automatic conversions can happen in 2 instances in java. What are they?

Answer 50

Java can automatically convert some primitive types to others and do so whenever necessary.

This automatic conversion is supported when the types are compatible with range and precision.

The original data type must have a smaller size in memory (and thus is capable of holding a smaller range in values) than the target type.

The target type must also hold the same or greater precision past the decimal point, so that there is no data lost in the conversion.

Whenever you perform a mathematical operation on two values that aren’t of the same type, Java automatically converts one of them to the type of the other.

Question 51

List Arithmetic operators

Answer 51

(+, -, *, /, %)

Question 52

List Logical operators

Answer 52

(&&, ||, !)

Question 53

List Comparison operators

Answer 53

(>, <, ==, >=, <=, !=)

Question 54

List Assignment operators

Answer 54

(=, +=, -=, *=, /=, %=)

Question 55

List Increment and decrement operators

Answer 55

(++, –)