Table of contents
1.
Introduction
2.
How does Dynamic Binding Work in Java?
3.
Limitations of Dynamic Binding in Java
4.
Difference between Static & Dynamic Binding
5.
Frequently Asked Questions
5.1.
Can dynamic binding be used with static methods?
5.2.
Is dynamic binding faster or slower than static binding?
5.3.
Can dynamic binding be used with private methods?
6.
Conclusion
Last Updated: Oct 18, 2024
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Dynamic Binding in Java

Author Sinki Kumari
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Introduction

In Java, binding refers to the process of linking a method call to the actual method implementation. There are two methods to do that. One of those methods is dynamic binding. 

Dynamic Binding in Java

Dynamic binding is a mechanism where the method implementation is selected based on the actual object type at runtime. This allows for polymorphism & flexibility in object-oriented programming. This feature enables polymorphism, which allows our code to handle different types of objects smoothly, which eventually increases flexibility and reusability in OOPS.

How does Dynamic Binding Work in Java?

Dynamic binding in Java occurs through inheritance & method overriding. When a subclass extends a superclass & overrides one of its methods, the overridden method in the subclass gets called at runtime based on the actual object type, not the reference type.
 

Let's say we have a superclass called Animal with a method makeSound(), & two subclasses Dog & Cat that override the makeSound() method. If we create an Animal reference variable but assign it a Dog object, calling makeSound() on that variable will invoke the overridden method in the Dog class. Similarly, if we assign a Cat object to the Animal reference, the makeSound() method of the Cat class will be called.
 

This behavior is possible because the JVM (Java Virtual Machine) determines the actual method to be called at runtime by checking the object's type. It looks for the overridden method in the object's class hierarchy, starting from the actual class of the object & moving up to its superclasses until a matching method is found.
 

Dynamic binding allows us to write more generic & reusable code by programming to an interface or superclass type while the specific implementation is determined dynamically based on the actual object.
 

For example : 

class Animal {
    public void makeSound() {
        System.out.println("Animal makes a sound");
    }
}
class Dog extends Animal {
    @Override
    public void makeSound() {
        System.out.println("Dog barks");
    }
}
class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("Cat meows");
    }
}
public class Main {
    public static void main(String[] args) {
        Animal animal1 = new Dog();
        Animal animal2 = new Cat();
        animal1.makeSound();
        animal2.makeSound();
    }
}
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Output

Dog barks
Cat meows


In this example, we have a superclass Animal with a method makeSound(). The Dog & Cat classes extend the Animal class & override the makeSound() method with their own implementations.

In the main() method, we create two Animal reference variables, animal1 & animal2, but assign them Dog & Cat objects respectively. When we call the makeSound() method on animal1, the overridden method in the Dog class is invoked, printing "Dog barks". Similarly, calling makeSound() on animal2 invokes the overridden method in the Cat class, printing "Cat meows".

Note: This example shows the dynamic binding, where the method that executes is determined at runtime based on the object’s actual type, even though the variable used to reference the object is of the superclass type, `Animal`.

Limitations of Dynamic Binding in Java

1. Dynamic binding only applies to instance methods. It does not work with static methods, private methods, or fields. These are resolved at compile-time using static binding.
 

2. Dynamic binding requires the methods to be overridden. If a method is not overridden in the subclass, the superclass method will be called, even if the subclass has a method with the same name but different parameters (method overloading).

 

3. Dynamic binding can have a slight performance overhead compared to static binding. The JVM needs to determine the actual method to call at runtime, which involves checking the object's class hierarchy. However, modern JVMs employ optimizations to minimize this overhead.
 

4. Dynamic binding relies on inheritance & method overriding. If a class is marked as `final`, it cannot be extended, & its methods cannot be overridden. Similarly, if a method is marked as `final`, it cannot be overridden in subclasses, limiting the applicability of dynamic binding.
 

5. Dynamic binding can lead to unexpected behavior if not used carefully. It's important to ensure that the overridden methods in subclasses adhere to the contract & expectations of the superclass method to avoid any surprises or inconsistencies.

Difference between Static & Dynamic Binding

FactorStatic BindingDynamic Binding
Time of ResolutionIn static binding, the method call is resolved at compile-time based on the reference type.In dynamic binding, the method call is resolved at runtime based on the actual object type.
Method OverridingStatic binding does not support method overriding. The method is determined by the reference type, regardless of overridden methods in the actual object's class.Dynamic binding supports method overriding. If a method is overridden, the overridden method in the actual object's class is called, allowing polymorphism.
ApplicabilityStatic binding applies to static methods, private methods, and fields. These members are resolved at compile-time based on the reference type.Dynamic binding applies to instance methods that are overridden in subclasses. The overridden method in the actual object's class is invoked at runtime.
PerformanceStatic binding is faster because the method call is resolved at compile-time, eliminating the need for runtime resolution.Dynamic binding has a small performance overhead due to runtime resolution, as the JVM determines the actual method to invoke based on the object's class hierarchy.
FlexibilityStatic binding provides less flexibility since the method call is based solely on the reference type, ignoring the actual object type.Dynamic binding provides more flexibility, allowing polymorphism. The method is determined based on the actual object type, enabling versatile and reusable code.
Use CasesStatic binding is used when the method call should be based on the reference type and no overriding is required. Suitable for fixed behaviors that do not depend on the actual object.Dynamic binding is used for polymorphic behavior, where the method implementation is dynamically determined based on the actual object type, allowing for flexible and extensible designs.

Frequently Asked Questions

Can dynamic binding be used with static methods?

No, dynamic binding does not apply to static methods. Static methods are resolved at compile-time using static binding.

Is dynamic binding faster or slower than static binding?

Dynamic binding has a slight performance overhead compared to static binding due to the runtime resolution of method calls.

Can dynamic binding be used with private methods?

No, dynamic binding does not work with private methods. Private methods are resolved at compile-time using static binding.

Conclusion

In this article, we discussed dynamic binding in Java & learned how it enables polymorphism by resolving method calls at runtime based on the actual object type. We saw examples of dynamic binding, understood its limitations, & compared it with static binding. Dynamic binding is a powerful feature in Java that allows for flexible & reusable code, which makes it easier to create extensible & maintainable object-oriented designs.

You can also check out our other blogs on Code360.

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