OBJECT ORIENTED PROGRAMMING THROUGH JAVA : Unit - 1 : Literal constants and Symbolic constants

What is a Constant?

A constant is a value that does not change during the execution of a program. It remains fixed.

Java supports two main types of constants:

1. Literal Constants

2. Symbolic Constants

1. Literal Constants

Definition:

Literal constants are the actual fixed values directly used in Java code. They are also called literals.

Key Point:

They are raw values written directly in the program and used without a name.

Types of Literal Constants:

Type	Description	Example
Integer Literal	Whole numbers without decimal. Can be in decimal, octal, or hexadecimal.	10, -99, 0x1A, 075
Floating Literal	Numbers with decimal or exponent.	3.14, 1.2e3, -0.5
Character Literal	Single character enclosed in single quotes.	'A', '9', '#'
String Literal	Group of characters enclosed in double quotes.	"Java", "123", " "
Boolean Literal	Logical constants for decision-making.	true, false
Null Literal	Special literal that represents "no object".	null

Examples of Literal Constants:

    int a = 10;           // 10 is an integer literal
    double pi = 3.14;     // 3.14 is a floating literal
char ch = 'A';        // 'A' is a character literal
String str = "Hello"; // "Hello" is a string literal
boolean flag = true;  // true is a boolean literal

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2. Symbolic Constants

Definition:

A symbolic constant is a named constant declared using the final keyword, which makes the value unchangeable after assignment.

Key Point:

It gives a name (symbol) to a value that doesn’t change – increasing readability and reusability.

🔸 Declaration Syntax:

final datatype CONSTANT_NAME = value;

🔸 Example:

final double PI = 3.14159;
final int MAX_AGE = 100;

🔸 Usage in Program:

public class CircleArea {
    public static void main(String[] args) {
        final double PI = 3.14159;
        int radius = 7;
        double area = PI * radius * radius;
        System.out.println("Area = " + area);
    }
}

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🔸 Difference Between Literal and Symbolic Constants

Feature	Literal Constant	Symbolic Constant
What it is	Fixed value written directly	Fixed value assigned to a named variable
Keyword used	None	final
Readability	Lower in complex code	Higher due to meaningful names
Reusability	Not reusable	Reusable throughout the code
Best Use Case	For single-use values	For values used multiple times
Example	3.14, "Hello"	final double PI = 3.14;

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Naming Convention for Symbolic Constants

                Use all uppercase letters.
     Use underscores to separate words.

✅ Examples:

final int MAX_MARKS = 100;

final double GRAVITY = 9.8;

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✅ Advantages of Symbolic Constants

✔ Improved readability of code.

✔ Avoids magic numbers (hard-coded values).

✔ Easier to update values in one place.

✔ Prevents accidental changes (value can't be modified).