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Exploring the Super Keyword in Java: Accessing Parent Class Methods and Constructors

The Super Keyword in Java

Java is a popular object-oriented programming language renowned for its flexibility and adaptability. It offers a range of features that aid in software development, and one such feature is the super keyword.

The super keyword provides developers with a way to access and invoke methods and constructors of a parent class from within the child class. This article will explore the primary uses of the super keyword, with a focus on accessing parent class methods and variables and invoking parent class constructors using the super() function.

Accessing Parent Class Methods and Variables

One of the primary uses of the super keyword in Java is accessing the methods and variables of a parent class within a child class. When creating a child class, Java allows developers to subclass a parent class, thereby inheriting its methods and variables.

However, in some instances, the child class may need to refer to a method or variable that exists within the parent class. The super keyword provides a way to do this by allowing the child class to access the parent class’s method or variable.

To do this, you simply place the keyword super in front of the method or variable’s name. When the child class invokes the method or variable, it does so from the parent class’s scope.

In this way, the super keyword acts as a reference to the parent class’s method or variable. Here is an example:

“`

public class Animal {

public void printSound() {

System.out.println(“Animal sound”);

}

}

public class Dog extends Animal {

public void printSound() {

super.printSound();

System.out.println(“Bark”);

}

}

public class Main {

public static void main(String[] args) {

Dog myDog = new Dog();

myDog.printSound();

}

}

“`

In this example, the parent class is Animal, and the child class is Dog.

Dog inherits Animal’s printSound() method, but adds some functionality to it by printing “Bark” in addition to “Animal sound”. The super keyword is used in this example inside Dog’s printSound() method to access Animal’s printSound() method.

The output of the myDog.printSound() method call will be:

“`

Animal sound

Bark

“`

From this example, you can see that the super keyword provides a way for the child class to access the parent class’s method and add its own functionality to it.

Invoking Parent Class Constructor using the super() function

Another use of the super keyword is to invoke the constructor of the parent class. When a child class is created, Java automatically calls the default constructor of the parent class.

However, if the parent class has a constructor with parameters, and the child class needs to invoke the constructor with parameters, the super() function can be used.

The super() function must be placed at the beginning of the child class’s constructor before any other statements.

If the parent class’s constructor has parameters, the super() function’s parameters must match those of the parent constructor. Here is an example:

“`

public class Teacher {

private String name;

public Teacher(String name) {

this.name = name;

}

}

public class Student extends Teacher {

private int id;

public Student(String name, int id) {

super(name);

this.id = id;

}

}

public class Main {

public static void main(String[] args) {

Student myStudent = new Student(“John Doe”, 1234);

System.out.println(myStudent.name);

System.out.println(myStudent.id);

}

}

“`

In this example, the parent class is Teacher, and the child class is Student.

Teacher has a constructor that takes a String parameter, while Student has a constructor that takes both a String and an int parameter. The super() function is used in Student’s constructor to invoke the Teacher constructor with the name parameter.

When myStudent is created, the constructor of Teacher is called through the super() function, which initializes the name variable to “John Doe”. The constructor of the Student class then initializes the id variable to 1234.

The output of the System.out.println statements will be:

“`

John Doe

1234

“`

From this example, you can see that the super() function provides a way for the child class to initialize the parent class before adding its own functionality to the constructor.

Conclusion

In conclusion, the super keyword in Java is used to access parent class methods and variables and to invoke parent class constructors using the super() function. The super keyword allows developers to add additional functionality to the parent class’s constructor, method, or variable without having to rewrite the code.

Additionally, the super() function provides a way to initialize the parent class before adding additional functionality required by the child class. Overall, the super keyword is an essential tool for software development in Java, as it helps to simplify the process of coding and makes software more flexible and adaptable.

In object-oriented programming, inheritance is a primary concept that allows us to create a new class by inheriting properties from an already existing class. In Java, this is done using the “extends” keyword, which creates a subclass or child class that inherits all the properties and methods from its parent or superclass.

The subclass can also have its own properties and methods, in addition to those inherited from the parent class. When creating a subclass in Java, it is important to have a clear understanding of how constructors work, particularly the parent and subclass constructors.

The parent constructor is the constructor of the parent class while the subclass constructor is the constructor of the subclass. Java provides a way to call the parent constructor from within the subclass constructor using the “super” keyword.

Let’s walk through some code to understand how the parent and subclass constructors work in Java and how to invoke the parent constructor using “super”. “`

public class Animal {

protected String name;

public Animal(String name) {

this.name = name;

}

public void noise() {

System.out.println(“Animal noise”);

}

}

public class Dog extends Animal {

private int age;

public Dog(String name, int age) {

super(name);

this.age = age;

}

public void noise() {

super.noise();

System.out.println(“Bark”);

}

}

public class Main {

public static void main(String[] args) {

Dog myDog = new Dog(“Fido”, 3);

System.out.println(myDog.name);

System.out.println(myDog.age);

myDog.noise();

}

}

“`

In this code, we have a parent class called “Animal” and a subclass called “Dog”.

The Animal class constructor takes in a parameter called “name”, which is then assigned to the “name” field. The subclass constructor, “Dog”, takes in two parameters: “name” and “age”.

The “name” parameter is passed to the parent constructor using the “super” keyword, while the “age” parameter initializes the subclass’s “age” field.

In the Main class, a new Dog object is created, with the name “Fido” and age 3.

Three subsequent lines of code print out various properties of the instantiated Dog object. The name and age fields are printed out, along with the results of the noise() method.

When the program executes, the following output is produced:

“`

Fido

3

Animal noise

Bark

“`

From this output, we can see that the constructor of the parent class is called first when an instance of the subclass is created. This is done through the use of the “super” keyword in the child class’s constructor.

In our example, the “super()” keyword is used in the Dog class’s constructor to call the Animal class’s constructor. The use of “super” in this way is important because it ensures that the parent class is initialized before the subclass.

Inheritance in Java works best when the parent class is correctly initialized before adding additional functionality to the subclass. By calling the parent class’s constructor first using “super”, we ensure the correct order of initialization.

In addition to invoking the parent constructor, the “super” keyword can also be used to call parent class methods. In the Dog class’s noise method, for example, the “super.noise()” statement is used to call the noise method of the Animal class before adding the “Bark” statement.

This allows us to inherit the behavior of the parent class’s noise method while also adding new functionality specific to the Dog subclass. In conclusion, the “super” keyword is an essential tool when working with subclass and parent constructors in Java.

It provides a way to invoke the parent class’s constructor and methods and helps ensure the proper order of initialization in subclass instances. By using the “super” keyword, developers can implement inheritance in Java more efficiently and effectively.

In conclusion, the “super” keyword plays a crucial role in Java programming, particularly when working with subclass and parent constructors. It enables developers to invoke parent class constructors and methods while ensuring the correct order of initialization in subclass instances.

The “super” keyword allows for the inheritance of parent class properties and methods in a subclass, helping to make Java code more efficient and organized. By understanding how to use “super,” developers can create clean and streamlined code that is easy to maintain and adapt.

The importance of using “super” in Java should not be overlooked, as it is essential for effective object-oriented programming.

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