Bounded type and wild cards

//BoundedType
public class BoundedArithematic<T extends Number> {
    public double add(T a, T b) {
        return a.doubleValue() + b.doubleValue();
    }
    public double subtract(T a, T b) {
        return a.doubleValue() - b.doubleValue();
    }
    public double multiply(T a, T b) {
        return a.doubleValue() * b.doubleValue();
    }	
   public double divide(T a, T b) {
        if (b.doubleValue() == 0) {
            throw new ArithmeticException("Division by zero is not allowed.");
        }
        return a.doubleValue() / b.doubleValue();
    }
    public static void main(String[] args) {
        BoundedArithematic<Number> calculator = new BoundedArithematic<>();
        Integer a = 10;
        Integer b = 5;
        System.out.println("Addition: " + calculator.add(a, b));
        System.out.println("Subtraction: " + calculator.subtract(a, b));
        System.out.println("Multiplication: " + calculator.multiply(a, b));
        System.out.println("Division: " + calculator.divide(a, b));
    }
}

//Wildcard Arguments
public class MagicBox<T> {
    private T item;

    public void addItem(T item) {
        this.item = item;
        System.out.println("Added item to the magic box: " + item);
    }

    public T getItem() {
                return item;
    }

    public void processBox(MagicBox<? super Integer> box) {
        System.out.println("Items in the box are processed["+box.getItem()+"]"); 
    }

    public static void main(String[] args) {
        
        MagicBox<Integer> integerBox = new MagicBox<>();
        integerBox.addItem(23);
        		
		MagicBox<String> stringBox = new MagicBox<>();
        stringBox.addItem("Shreya");
        	
		
        MagicBox<Boolean> booleanBox = new MagicBox<>();
        booleanBox.addItem(false);
        
		MagicBox<Object> dobubleBox = new MagicBox<>();
        dobubleBox.addItem(23.43);
		
		integerBox.processBox(integerBox);
		dobubleBox.processBox(dobubleBox);
		
		
		
        
    }
}