Java - symbolic constants

In Java, symbolic constants are fixed values represented by meaningful names, rather than hard-coded values, which improves code readability and reliability. Java commonly uses final variables and enums to define symbolic constants. It's of various uses:

• Makes programs easier to maintain
• Prevents accidental modification of values
• Eliminates magic numbers
• Enhances consistency across the application

public class GFG {
    static final int MAX_AGE = 60;

    public static void main(String[] args)
    {
        System.out.println("Maximum allowed age is: "
                           + MAX_AGE);
    }
}

Maximum allowed age is: 60

Explanation:

• MAX_AGE is declared as a symbolic constant using static final
• final ensures the value cannot be modified
• static allows access without creating an object
• Using a meaningful name improves code readability and maintenance

Symbolic Constants Using the final Keyword

In Java, a variable declared with the final keyword becomes a constant, meaning its value cannot be changed once assigned.

Syntax:

final dataType CONSTANT_NAME = value;

Using static final for Class-Level Constants

The combination of static and final is commonly used to define class-level symbolic constants.

class GFG {
    public static final double PI = 3.14159;

    public static void main(String[] args) {
        System.out.println("Value of PI: " + PI);
    }
}

Value of PI: 3.14159

Explanation:

• static ensures a single shared copy
• final prevents reassignment
• Constants can be accessed using the class name

Symbolic Constants Using enum

For a fixed set of related constants, Java provides the enum type. Enums are type-safe than final variables.

enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY
}

class GFG {
    public static void main(String[] args) {
        Day today = Day.MONDAY;
        System.out.println(today);
    }
}

MONDAY

Explanation: Enums represent a predefined set of constants and provide better compile-time safety.

Naming Conventions for Symbolic Constants

Symbolic constants should be written in uppercase letters, with multiple words separated by underscores (_). They should be declared as static final to ensure immutability and class-level access.

public class GFG {

    // Symbolic constant
    public static final int MAX_AGE = 60;

    public static void main(String[] args)
    {
        int userAge = 45;

        if (userAge <= MAX_AGE) {
            System.out.println("User is eligible.");
        }
        else {
            System.out.println("User is not eligible.");
        }
    }
}

User is eligible.

Explanation:

• MAX_AGE is a symbolic constant declared using public static final
• Its value cannot be changed after initialization
• The constant is accessed directly using the class name
• Replacing hard-coded values improves clarity and maintainability

final vs enum