Static vs Dynamic Binding in Java

There are certain key points that are needed to be remembered before adhering forward where we will be discussing and implementing static and dynamic bindings in Java later concluding out the differences.  

• private, final and static members (methods and variables) use static binding while for virtual methods (In Java methods are virtual by default) binding is done during run time based upon the run time object.
• The static binding uses Type information for binding while Dynamic binding uses Objects to resolve to bind.
• Overloaded methods are resolved (deciding which method to be called when there are multiple methods with the same name) using static binding while overridden methods use dynamic binding, i.e, at run time.

Static Binding

The binding which can be resolved at compile time by the compiler is known as static or early binding. The binding of all the static, private, and final methods is done at compile-time.

Example:

print() in superclass is called
print() in superclass is called

Output Explanation: As you can see, in both cases the print method of the superclass is called. Let us discuss how this happens 

• We have created one object of subclass and one object of the superclass with the reference of the superclass.
• Since the print method of the superclass is static, the compiler knows that it will not be overridden in subclasses and hence compiler knows during compile time which print method to call and hence no ambiguity.

As an exercise, the reader can change the reference of object B to subclass and then check the output. 

Dynamic Binding

In Dynamic binding compiler doesn't decide the method to be called. Overriding is a perfect example of dynamic binding. In overriding both parent and child classes have the same method.

Example:

print in superclass is called
print in subclass is called

Output Explanation: Here the output differs. But why? Let's break down the code and understand it thoroughly. 

• Methods are not static in this code.
• During compilation, the compiler has no idea as to which print has to be called since the compiler goes only by referencing variable not by the type of object, and therefore the binding would be delayed to runtime and therefore the corresponding version of the print will be called based on type on an object.

Tip: Geeks, now the question arises why binding of static, final, and private methods is always static binding? 

Static binding is better performance-wise (no extra overhead is required). The compiler knows that all such methods cannot be overridden and will always be accessed by objects of the local class. Hence compiler doesn’t have any difficulty determining the object of the class (local class for sure). That’s the reason binding for such methods is static. 

Let us now finally see the differences between static and dynamic binding that is as follows: