Starting with variables

Introduction to Java

Jim White

Java Developer

Variables are boxes

A box with books

Variables are boxes

A box with kitchen essentials

Allow to store different kinds of information
Have a type, a name, and a value

Assigning variables - String keyword

String

Components:

String keyword

Assigning variables - name

String variableName

Components:

String keyword
Variable name

Assigning variables - syntax

String variableName =

Components:

String keyword
Variable name
= to assign value

Assigning variables - text

String variableName = "text in double quotation marks";

Components:

String keyword
Variable name
= to assign value
The actual value
Semicolon ;

String message = "Hello, Java!";

Assigning variables - whole numbers

Use int for whole numbers

int age = 29;

Single equal sign

Doesn't mean mathematical equal ❌

Mathematical equal

Assignment operator ✅

Putting books into the box

Declaring variables

Always specify the data type
- Text -> String
- Number -> int

Other data types: char, boolean, float, and more

Exclamation sign

Naming convention

Good variable names:

int age = 31;

String welcomeMessage = "Hello";


String daysToSummer = "Too many";

String myName = "Jim";

Use camelCase: lowercase first word, capitalize next words

Bad variable names:

int 4age = 31;          

String welcome message = "Hello";


String days_to_summer = "Too many"; 

String MyName = "Jim";

Using variables

class InfoAboutJava {
  public static void main(String[] args) {


    String message = "Java is awesome!";


    // Print the message variable
    System.out.println(message);

    }
}

Java is awesome!

Summary

Variables store values
type variableName = value;
Variable names:
- Start with letter
- Follow camelCase
- Cannot contain space

Use variables instead of their value

class InfoAboutJava {
public static void main(String[] args) {  

  String message = "Java is awesome!";

  // Using variable directly
  System.out.println(message);
  }
}

Let's practice!

Introduction to Java