Java Basics

1. Getting Started

In this section, you will get acquainted with Java, understand its peculiarities, and why I would recommend learning this particular programming language. You will write your first Java code and familiarize yourself with printing text to the console. Shall we begin?

Backend Development

Role of Java in the Backend

2. Basic Types, Operations

We have completed a theoretical course, and now the most interesting part begins. In this section, we will familiarize ourselves with the basics of coding, primitive data types, and operations on them. Now your code can perform mathematical tasks and evaluate conditions for further execution. Sounds interesting? Let's start getting acquainted.

Primitive Data Types

Primitive Types Challenge

Char and ASCII Table (bonus)

Mathematical Operations in Java

If-Else Statement

Switch-Case Statement

Weekday Switch Challenge

3. Loops

In this section, we will familiarize ourselves with various loops such as for, while, and do-while. Loops are essential to any programming language, as they allow us to efficiently iterate over a large amount of data and save significant time. Later on, you will use loops extensively in tasks like sorting, working with arrays, collections, and more. Well then, let's get started.

Introduction to Loops

While-Loop

Do-While Loop

For-Loop

Increment and Decrement

Infinite Loop (bonus)

Challenge: Factorial

4. Arrays

This section will cover arrays and how to use them correctly. We will learn how to group data into arrays and explore some methods for working with arrays. Arrays are essential to any programming language Java, so let's dive in.

What is Array?

Using Loops with Arrays

Index Out Of Bounds

Two-Dimentional Array

Iteration In Two-Dimensional Array

For-Each Loop

5. String

In this section, you will be introduced to a data type called String. Why is there a separate section in the course for this data type? String is a significant data type with many built-in methods and operations. In this course, you will learn about String and StringBuilder, explore their basic methods, and learn how to use strings effectively in Java. So, are you ready to get started?

What Is String?

Basic Methods In String Part 1

Basic Methods In String Part 2

B-Inclusion Filter Challenge

NullPointer Exception

StringBuilder

String Pool, Method Equals()

Summary

Primitive Data Types

Variables

A variable in code is a kind of cell where we can store information. For example, if we need to save the number 20, we will save it in a variable and use this number again simply by using the variable name in the code.

Java is a strongly typed language, so we are required to define the data type of our variable:

Main.java

The code above illustrates the basic syntax for declaring a variable.

Now, let's proceed to the study of data types, beginning with the 8 primary ones.

Data Types

Data type determines the kind of data that will be stored in a container called a variable. There are three types of data: numeric, textual, and boolean. Numeric data types include byte, short, int, long, float, and double. Textual data types are char and String, and boolean data types include boolean.

Note
Note that the String data type is not a primitive data type, so we won't cover it in this section. It has a separate section where you will learn about this data type in detail.

Let's go through primitive data types and learn more about each of them:

byte - This integer data type can accept values ranging from -128 to 127. It occupies 1 byte of memory and is stored in the stack memory;

Main.java

short - is also an integer data type that can hold values ranging from -32,768 to 32,767. It occupies 2 bytes of memory and is stored in the stack memory;

Main.java

int - This is the most commonly used integer data type, capable of holding values ranging from -2,147,483,648 to 2,147,483,647. It is also stored in the stack memory and occupies 4 bytes;

Main.java

long - This is the largest integer data type, capable of storing values from -2⁶³ to 2⁶³ - 1. It occupies 8 bytes in memory and is also stored in the stack memory;

Main.java

float - is the first floating-point data type to store 7 decimal digits. When declaring a variable of type float, we must remember to append the letter f at the end of the number. For example, float myFloat = 4.13f;;

Main.java

double - This floating-point data type can store up to 15 decimal digits. Unlike float, we don't need to specify letters when declaring a double variable. Double occupies 8 bytes and is stored in the stack memory;

Main.java

boolean - This primitive data type is special as it can only hold true or false values. Boolean is stored in the stack memory and occupies from 1 bit to 1 byte, depending on the system and compiler;

Main.java

char - This character data type takes data from the ASCII table. We will delve into this data type in more detail in the next chapter, but for now, please note that it occupies 2 bytes.

Main.java

There is also a table where you can view all the essential information about primitive data types:

Data Type	Range	Size (in bytes)	Memory Location
byte	-128 to 127	1	Stack
short	-32,768 to 32,767	2	Stack
int	-2³¹ to 2³¹ - 1	4	Stack
long	-2⁶³ to 2⁶³-1	8	Stack
float	-2⁻¹⁴⁹ to (2 - 2⁻²³) * 2¹²⁷	4	Stack
double	-2⁻¹⁰⁷⁴ to (2 - 2⁻⁵²) * 2¹⁰²³	8	Stack
boolean	true or false	1 bit to 1 byte	Stack
char	0 to 2¹⁶ - 1	2	Stack

Primitive data types can also be output using the console output command. Let's examine some examples:

Main.java

We declared an int variable and printed it on the screen.

Main.java

We declared a char variable and printed it on the screen.

Main.java

We declared a float variable and printed it on the screen.

Note
We don't need to wrap variables in double quotation marks as we did when outputting text using System.out.println().

1. Which integer data type occupies the least amount of memory?

2. What data type can have only two values: ``true`` or ``false``?

Everything was clear?

Section 2. Chapter 1

Primitive Data Types

Variables

Java is a strongly typed language, so we are required to define the data type of our variable:

Main.java

The code above illustrates the basic syntax for declaring a variable.

Now, let's proceed to the study of data types, beginning with the 8 primary ones.

Data Types

Note
Note that the String data type is not a primitive data type, so we won't cover it in this section. It has a separate section where you will learn about this data type in detail.

Let's go through primitive data types and learn more about each of them:

byte - This integer data type can accept values ranging from -128 to 127. It occupies 1 byte of memory and is stored in the stack memory;

Main.java

short - is also an integer data type that can hold values ranging from -32,768 to 32,767. It occupies 2 bytes of memory and is stored in the stack memory;

Main.java

int - This is the most commonly used integer data type, capable of holding values ranging from -2,147,483,648 to 2,147,483,647. It is also stored in the stack memory and occupies 4 bytes;

Main.java

long - This is the largest integer data type, capable of storing values from -2⁶³ to 2⁶³ - 1. It occupies 8 bytes in memory and is also stored in the stack memory;

Main.java

float - is the first floating-point data type to store 7 decimal digits. When declaring a variable of type float, we must remember to append the letter f at the end of the number. For example, float myFloat = 4.13f;;

Main.java

double - This floating-point data type can store up to 15 decimal digits. Unlike float, we don't need to specify letters when declaring a double variable. Double occupies 8 bytes and is stored in the stack memory;

Main.java

boolean - This primitive data type is special as it can only hold true or false values. Boolean is stored in the stack memory and occupies from 1 bit to 1 byte, depending on the system and compiler;

Main.java

char - This character data type takes data from the ASCII table. We will delve into this data type in more detail in the next chapter, but for now, please note that it occupies 2 bytes.

Main.java

There is also a table where you can view all the essential information about primitive data types:

Data Type	Range	Size (in bytes)	Memory Location
byte	-128 to 127	1	Stack
short	-32,768 to 32,767	2	Stack
int	-2³¹ to 2³¹ - 1	4	Stack
long	-2⁶³ to 2⁶³-1	8	Stack
float	-2⁻¹⁴⁹ to (2 - 2⁻²³) * 2¹²⁷	4	Stack
double	-2⁻¹⁰⁷⁴ to (2 - 2⁻⁵²) * 2¹⁰²³	8	Stack
boolean	true or false	1 bit to 1 byte	Stack
char	0 to 2¹⁶ - 1	2	Stack

Primitive data types can also be output using the console output command. Let's examine some examples:

Main.java

We declared an int variable and printed it on the screen.

Main.java

We declared a char variable and printed it on the screen.

Main.java

We declared a float variable and printed it on the screen.

Note
We don't need to wrap variables in double quotation marks as we did when outputting text using System.out.println().

1. Which integer data type occupies the least amount of memory?

2. What data type can have only two values: ``true`` or ``false``?

Everything was clear?

Section 2. Chapter 1