Super Keywords in Java: Everything You Need to Know

If you're learning to program in Java, the lingo can seem overwhelming. There are so many terms, like class, method, constructor, and “super keywords.” However, there's no need to worry. This jargon doesn't take long to become second nature with a bit of practice.

Think of learning super keywords as putting together a giant puzzle. Each piece is important and serves its own distinct purpose. Below we’ll dive into everything you should know about super keywords and how you can leverage their power.

Table of Contents

• What is a super keyword in Java?
• The Benefits of Using a Super Keyword
• When to Use Super Keywords in Java
• How to Use Super Keywords in Java

Let's use a house as a metaphor to explain super keywords in Java. The superclass of a house could be the foundation, which is the large piece of concrete that acts as the base for all its walls and other components. This superclass contains elements like structural integrity and stability — traits that are vital to any home’s success.

When the super keyword is used, it allows access to all of the superclass’s components. In this case, the super keyword would allow a developer to draw upon the superclass's structural integrity and stability features (the foundation) to construct new classes like walls, windows, and doors.

The Benefits of Using a Super Keyword in Java

With super keywords, developers can access superclass elements easily, which can help save time when creating new classes. This offers a way for developers to reuse code while reducing redundancy in their projects.

With super keywords, you can create a robust program more quickly with fewer bugs and errors. Here are four benefits of using super keywords.

1. Super keywords improve code readability.

Using super keywords in your code lets you easily indicate which variables and methods are inherited from the parent class. This clarifies where specific properties are coming from and helps with code documentation.

Using “super” also makes reading and understanding your code easier. This can be especially helpful when working on a collaborative project with team members.

2. You’ll avoid variable name conflicts.

If you have a variable with the same name as an instance variable in the parent class, you can use “super” to reference the parent class variable. This helps avoid naming conflicts and makes your code more readable.

3. You can implement polymorphism.

Polymorphism allows objects to be treated like they are of many different types, even if they share the same underlying properties or methods. You can then write reusable code that works with objects of different types.

Super keywords help to implement polymorphism by enabling a subclass object to be treated like a parent class object. This is useful when you want to pass an instance of a subclass to a method that expects an instance of the parent class.

4. Super keywords allow you to invoke parent class constructors.

When creating an instance of a subclass, you can use “super” to call the parent class constructor. This helps avoid code duplication and enhances code usability.

Using “super” to call the parent constructor also ensures that the superclass properties are initialized before the subclass properties, which is necessary for some constructors in Java.

When to Use Super Keywords in Java

You can use the “super” keyword in Java to access or use the properties, methods, or constructors of the parent class from the subclass. It’s particularly useful when you want to override a method or constructor in a subclass, while maintaining the functionality present in the parent class.

We’ll discuss more specific instances where developers could use super keywords below.

1. Constructors

Constructors are used to create objects that share a similar set of properties and methods. When a constructor is called with the “new” keyword, it creates and returns a new instance of the object with the properties and methods defined within the constructor.

Super keywords in Java can be used to call superclass constructors. This is useful when creating derived classes, as it allows you to use the superclass constructor’s parameters when creating the object. The syntax for using super keywords in constructors follows:

By calling the parent class constructor with “super,” you can ensure that the parent properties are initialized correctly and that your subclass can inherit and use those properties. Additionally, using “super” when constructing a subclass object allows you to avoid duplicating code that is present in the parent class constructor.

2. Overriding superclass methods

In Java, a superclass is the parent class of a subclass. Superclass methods are defined in the superclass and inherited by the subclass. This subclass can then use superclass methods in addition to its own methods.

Superclass methods can be accessed and overridden by the subclass using the “super” keyword. For example, if you want to provide different behavior for a method in your subclass, you can write a new version of the method and use super to call the superclass’s version:

3. Accessing superclass variables

Superclass variables can help developers maintain encapsulation, reuse code, and improve their code's readability. Super keywords in Java can be used to access these superclass variables, which is useful if you need to use the superclass’s variable in your derived class.

If you’re looking to access superclass variables with super keywords, try the following code:

How to Use Super Keywords in Java

1. Identify the subclass and superclasses that you want to work with.

To use the “super” keyword in a subclass, you first need to create a superclass. This class should contain the properties and methods you want to inherit in the subclass.

After creating the superclass, you can create a subclass that extends the superclass. This is done with the “extends” keyword and the superclass's name.

2. Identify what you want to do with the super keyword.

Once you've created the subclass, you can define a method or constructor that you want to use the “super” keyword in. This method or constructor can either be new or overridden.

Determine if you need to call a superclass constructor, override superclass methods, or access superclass variables.

3. Use “super” to access or override superclass properties.

Within the overridden method or constructor, you can use the “super” keyword to access the properties or methods of the superclass. In Java, super keywords should be preceded by the keyword super and followed by parentheses (if needed).

For example, if you want to retrieve a superclass instance variable, you could use “super.variableName”. If you want to call a superclass method, use “super.methodName()”.

Suppose you want to override a superclass method in the subclass. You can use the “super” keyword to retain the functionality of the superclass method while adding new functionality to the subclass method.

To do this, call the superclass method with “super.methodName()”. Then, add any additional functionality that you want in the subclass method.

4. Compile and run your code.

After using the “super” keyword in the subclass, compile and run the Java program to see the results. Always run your code through a program tester before you deploy it.

For example, if you want to use super in a constructor:

Leveraging the Power of Super Keywords

Super keywords in Java are incredibly powerful tools for developers, allowing access to superclass elements and methods. By leveraging the power of super keywords, you can save time when creating new classes by reusing code and reducing redundancy in your projects.

Super keywords help create more robust programs with fewer bugs and errors due to using superclass elements. With this knowledge, you can confidently apply super keyword techniques to your own programming projects.