Also called late binding, this refers to Java choosing the proper method to call at run time, as opposed to at compile time.
For example, suppose Rectangle and Circle both extend the class Shape:
Shape rect = new Rectangle(10, 20);
Shape circ = new Circle(30);
// Rectangle's version of getArea will be called
double area1 = rect.getArea();
// Circle's version of getArea will be called
double area2 = circ.getArea();The proper version of getArea ends up being called, because it is decided at run time. This is dynamic binding.
If it were decided at compile time, then Shape’s version of getArea would be called, because at compile time the object type is Shape. But we want the more specific version (Circle or Rectangle’s version of getArea), depending on the type of the object at run time.