Variables

⇒ Variables are like containers used for storing data values.

# Declaring Variable

int varibaleName = variable_Value;

# Ex :-
int age = 12;

Data Types

⇒

Naming Conventions

⇒ camelCase

→ Start with a lowercase letter. Capitalize the first letter of each subsequent word.

→ Example: myVariableName

⇒ snake_case

→ Start with an lowercase letter. Separate words with underscore

→ Example: my_variable_name

⇒ Kebab-case

→ All lowercase letters. Separate words with hyphens.

→ Example: my-variable-name

⇒ Keep a Good and Short Name

→ Choose names that are descriptive but not too long. It should make it easy to understand the variable's purpose.

→ Example: age, firstName, isMarried

Identifier Rule

⇒ The only allowed characters for identifiers are all alphanumeric characters([A-Z],[a-z],[0-9]), ‘$‘ (dollar sign) and ‘_‘ (underscore).

⇒ Can’t use keywords or reserved words

⇒ Identifiers should not start with digits([0-9])

⇒ Java identifiers are case-sensitive.

⇒ There is no limit on the length of the identifier but it is advisable to use an optimum length of 4 – 15 letters only.

Literals

⇒ Integer

→ 10, 5, -8, etc…

⇒ Floating Points

→ 1.2, 0.25, -0.999, etc…

⇒ Boolean

→ true, false

⇒ Character

→ ‘a’, ‘b’, ‘A’, ‘N’, etc…

⇒ String

→ “hi”, “hello”, etc…

Keywords

⇒ abstract assert boolean break byte case catch char class const* continue default do double else enum extends final finally float for goto* if implements import instanceof int interface long native new package private protected public return short static strictfp super switch synchronized this throw throws transient try void volatile while

<aside> 🔒

• const and goto are reserved but not used in Java.

</aside>

Escape Sequences

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello\\nWorld");      // Line break
        System.out.println("Hello\\tWorld");      // Tab space
        System.out.println("He said, \\"Hi!\\"");  // Double quotes
        System.out.println("Path: C:\\\\Java\\\\");  // Backslash
    }
}

User Input

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
       System.out.print("Enter Your name: ");
       String name = input.nextLine();
       System.out.print("Welcome " + name);
    }
}

Type Conversion and Casting

⇒ Image