The following example code demonstrates How to Perform Runtime Polymorphism in Java.

Create a class Shape containing three methods – area(), draw(), and erase(). Also, create its three subclasses – Circle, Rectangle, and Triangle. Demonstrate the runtime polymorphism using these classes.

Here’s an example of creating a class `Shape` and its subclasses `Circle`, `Rectangle`, and `Triangle` in Java.

``````abstract class Shape {
abstract void area();
void draw() {
System.out.println("Drawing Shape");
}
void erase() {
System.out.println("Erasing Shape");
}
}

class Circle extends Shape {
void area() {
System.out.println("Calculating area of Circle");
}
void draw() {
System.out.println("Drawing Circle");
}
void erase() {
System.out.println("Erasing Circle");
}
}

class Rectangle extends Shape {
void area() {
System.out.println("Calculating area of Rectangle");
}
void draw() {
System.out.println("Drawing Rectangle");
}
void erase() {
System.out.println("Erasing Rectangle");
}
}

class Triangle extends Shape {
void area() {
System.out.println("Calculating area of Triangle");
}
void draw() {
System.out.println("Drawing Triangle");
}
void erase() {
System.out.println("Erasing Triangle");
}
}
``````

And here’s an example of using these classes to demonstrate runtime polymorphism.

``````class Test {
public static void main(String args[]) {
Shape s;
s = new Circle();
s.area();
s.draw();
s.erase();
s = new Rectangle();
s.area();
s.draw();
s.erase();
s = new Triangle();
s.area();
s.draw();
s.erase();
}
}
``````

In this code, the class `Shape` is defined as an abstract class with three methods `area()`, `draw()`, and `erase()`. The subclasses `Circle`, `Rectangle`, and `Triangle` extend the `Shape` class and provide their own implementation of the `area()` method. The class `Test` uses the references of `Shape` class to hold objects of its subclasses, which demonstrates runtime polymorphism. When the methods `area()`, `draw()`, and `erase()` are called using the references of `Shape`, the JVM calls the corresponding methods in the actual objects.