Program 8 : Enum & Autoboxing

Develop a Java program that uses enumerations and demonstrates autoboxing with type wrappers.

• The Day enum now has a constructor and a private field (dayValue) to store an integer for each day.

• New methods have been added to the enum:

  • getDayValue(): A getter to retrieve the day's number.

  • isWeekend(): An operation that returns true if the day is a weekend.

• The main method has been updated to demonstrate these new capabilities.

public class EnumAndAutoboxingDemo {

    // The enum with constructor, field, and methods.
    public enum Day {
        // Each constant now calls the constructor to set its integer value.
        SUNDAY(1),
        MONDAY(2),
        TUESDAY(3),
        WEDNESDAY(4),
        THURSDAY(5),
        FRIDAY(6),
        SATURDAY(7);

        // A private final field for the day's value.
        private final int dayValue;

        // Enum constructors are implicitly private.
        Day(int value) {
            this.dayValue = value;
        }

        // A getter method to access the day's value.
        public int getDayValue() {
            return this.dayValue;
        }

        // An operation based on the enum constant.
        public boolean isWeekend() {
            return (this == SATURDAY || this == SUNDAY);
		// 'this' refers to constant on which method is called.
        }
    }
    
    public static void main(String[] args) {
        System.out.println("--- Demonstrating Enumerations with Values and Methods ---");
        
        Day today = Day.WEDNESDAY;
        System.out.println("Today is: " + today);
        
        System.out.println("Day number for " + today 
	        + " is: " + today.getDayValue());
        
        System.out.println("Is " + today 
	        + " a weekend? " + today.isWeekend());

        System.out.println("\n--- Iterating through all days ---");
        for (Day day : Day.values()) {
            System.out.printf("Day: %-10s | Value: %d | Is Weekend? %s\n",
                day, day.getDayValue(), day.isWeekend());
        }
	        
	        
        System.out.println("\n--- Demonstrating Autoboxing ---");
        new AutoBox();
    }
    
    static class AutoBox {
         public AutoBox() {
            Integer iOb = 99;
            System.out.println("Original value of iOb: " + iOb);
            
            ++iOb; // unboxed, incremented, reboxed
            System.out.println("After ++iOb: " + iOb);
            
            iOb += 10; // unboxed, added, reboxed
            System.out.println("After iOb += 10: " + iOb);
            
            Integer iOb2 = iOb + (iOb / 3); 
            // unboxed, computed, reboxed
            System.out.println("iOb2 after expression: " + iOb2);
            
            int i = iOb + (iOb / 3); 
            // unboxed, result stored as primitive
            System.out.println("i after expression: " + i);
        }
    }
}

Output

--- Demonstrating Enumerations with Values and Methods ---
Today is: WEDNESDAY
Day number for WEDNESDAY is: 4
Is WEDNESDAY a weekend? false

--- Iterating through all days ---
Day: SUNDAY     | Value: 1 | Is Weekend? true
Day: MONDAY     | Value: 2 | Is Weekend? false
Day: TUESDAY    | Value: 3 | Is Weekend? false
Day: WEDNESDAY  | Value: 4 | Is Weekend? false
Day: THURSDAY   | Value: 5 | Is Weekend? false
Day: FRIDAY     | Value: 6 | Is Weekend? false
Day: SATURDAY   | Value: 7 | Is Weekend? true

--- Demonstrating Autoboxing ---
Original value of iOb: 99
After ++iOb: 100
After iOb += 10: 110
iOb2 after expression: 146
i after expression: 146

---

public class EnumAndAutoboxingDemo {

    public enum Day {
        SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
    }
	
    public static void main(String[] args) {
        System.out.println("--- Demonstrating Enumerations ---");
		
        // Assigning a value from the enum
        Day today = Day.WEDNESDAY;
        System.out.println("Today is: " + today);

        System.out.println("\nIterating through all days of the week:");
        for (Day day : Day.values()) {
            System.out.println(day);
        }
		
        // --- Autoboxing and Auto-unboxing Demonstration ---
        System.out.println("\n--- Demonstrating Autoboxing ---");

        Integer integerObject = 100;
        System.out.println("Value of Integer object: " 
	        + integerObject);

		new AutoBox();
		//AutoBox unbox = new AutoBox();
		//unbox.boxUnbox();
    }
	
	static class AutoBox {
		 public AutoBox() {
	        Integer iOb = 99;
	        System.out.println("Original value of iOb: " + iOb);
			
	        ++iOb; // unboxed, incremented, reboxed
	        System.out.println("After ++iOb: " + iOb);
			
	        iOb += 10; // unboxed, added, reboxed
	        System.out.println("After iOb += 10: " + iOb);
			
	        Integer iOb2 = iOb + (iOb / 3); 
	        // unboxed, computed, reboxed
	        System.out.println("iOb2 after expression: " + iOb2);
			
	        int i = iOb + (iOb / 3); 
	        // unboxed, result stored as primitive
	        System.out.println("i after expression: " + i);
	    }
	}
}

Output

--- Demonstrating Enumerations ---
Today is: WEDNESDAY

Iterating through all days of the week:
SUNDAY
MONDAY
TUESDAY
WEDNESDAY
THURSDAY
FRIDAY
SATURDAY

--- Demonstrating Autoboxing ---
Value of Integer object: 100
Original value of iOb: 99
After ++iOb: 100
After iOb += 10: 110
iOb2 after expression: 146
i after expression: 146