访问者模式-Visitor Pattern

The Visitor pattern is a behavioral design pattern that allows you to separate algorithms from the objects on which they operate. It enables you to add new operations to existing object structures without modifying those structures. This pattern is particularly useful when you have a complex object structure with different types of objects and you need to perform various operations on these objects.

Here's an example of the Visitor pattern implemented in Java:

// Visitor interface
interface Visitor {
    void visit(Circle circle);
    void visit(Rectangle rectangle);
}

// Concrete visitor implementation
class AreaVisitor implements Visitor {
    @Override
    public void visit(Circle circle) {
        double area = Math.PI * circle.getRadius() * circle.getRadius();
        System.out.println("Area of Circle is: " + area);
    }

    @Override
    public void visit(Rectangle rectangle) {
        double area = rectangle.getWidth