Java extend multiple classes

In Java, what does extend mean?

One of several Java inheritance keywords is extended, meaning we pass all or most of the Parent class's characteristics through to the Child class.

The class from which we use such characteristics is known as the Child class, and the object through which we inherited the characteristics like constants and procedures is known as the Parent class.

We may frequently require the identical characteristics that we have already honed in other classes. Therefore, if we can reuse such attributes from other classes rather than constructing them from scratch, we can save time and memory. Similarly, by extending a class in Java, we may utilize more class properties in our class.

Assume we own a firm that manufactures mobile devices. To create various sorts of mobile devices, we could require various elements from this company, such as processors, batteries, cables, and other components found in most mobile devices. Therefore, we can construct the same components with basic functionality so that we may use them.

A Java OOPs feature called inherited enables extending a class to another class to access a class's characteristics. There is a restriction on Java's ability to extend classes to other classes. It implies that a class could only extend one other class at once. Multiple class extensions will result in unsuccessful code execution.

Single inheritance occurs when a class extends another class. A class extending several classes is known as multi-inheritance, which is prohibited in Java.

In Java, can we extend classes?

No, Java does not allow us to extend multiple classes. We cannot extend several classes in Java since it does not enable multiple inheritances. Only one class can be extended, and numerous Interfaces can be used.

We may specify abstract fields in interfaces by utilizing the implement keyword in Java and subsequently reference them in child classes. We can implement multiple inheritances in Java in this way.

Why Can't Multiple Classes be Extended in Java?

Due to duplication, extending more than one class in Java is not feasible. Redundant data may develop if Java permits the extension of several classes.

Even so, there are other options than extending several classes. However, let's imagine that you may employ the perform() function in a child class since you used it in two separate classes, Class Both a Class B. Therefore, it is impossible to distinguish between the class method you want to invoke when calling that method from a child class.

Extend 2 classes in Java

A class extends 2 classes throughout this sample technique, indicating multiple inheritances. The program does not run and generates a compile time error since Java does not permit this procedure. See the illustration below.

Example: SimpleTestings.java

class Running{
    int speeds;
    void showSpeeds() {
        System.out.println("The present Speed is "+speeds);
    }
}
class Cars{
    String colors;
    int topSpeeds;
}
public class SimpleTestings extends Running,Cars{
    public static void main(String[] args) {
        SimpleTestings runs = new SimpleTestings();
        runs.showSpeeds();
        runs.speeds = 20;
        runs.showSpeeds();
    }
}

Output                                         

/tmp/CjX8EtVMiF/SimpleTestings.java:11: error: '{' expected
class SimpleTestings extends Running, Cars{
                                    ^
1 error

The program throws a compilation error as two classes can’t be extended.

Extension of the Interfaces in Java

Java prohibits using two classes. However, a class may extend two interfaces. A class may extend multiple interfaces using this technique. This code runs without any issues and executes correctly. Therefore, it would be preferable to utilize the interface if you wanted to extend several inheritances. See the illustration below.

Example: Interface.java

interface Running{
    int speeds = 1000;
    static void showSpeeds() {
        System.out.println("The present Speed is :"+speeds);
    }
}


interface Cars{
    String colors = "Yellow";
    int topSpeeds = 10000;
}


public class Interface implements Running, Cars{
    public static void main(String[] args) {
       Interface runs = new Interface();
        Running.showSpeeds();
        System.out.println("The highest Speed is "+Cars.topSpeeds);
    }
}

Output

The present Speed is :1000
The highest Speed is 10000

In this way, the extension of multiple classes in java is possible by using the interface concept.