Java Program to Implement Shape Interface using Circle and Rectangle Class

This is a Java Program to Make Shape as an Interface and Implement it using Circle and Rectangle Class.

Interfaces are syntactically similar to classes, but they lack instance variables, and their methods are
declared without any body. Here we make interface as Shape with two methods as input() and area() which are implemented by further two classes as circle and rectangle who implements the interface Shape.

Here is the source code of the Java Program to Make Shape as an Interface and Implement it using Circle and Rectangle Class. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

```
interface Shape
```
```
{
```
```
    void input();
```
```
    void area();
```
```
}
```
```
class Circle implements Shape
```
```
{
```
```
    int r = 0;
```
```
    double pi = 3.14, ar = 0;
```
```
    @Override
```
```
    public void input()
```
```
    {
```
```
        r = 5;
```
```
    }
```
```
    @Override
```
```
    public void area()
```
```
    {
```
```
        ar = pi * r * r;
```

        System.out.println("Area of circle:"+ar);

```
    }
```
```
}
```
```
class Rectangle extends Circle
```
```
{
```
```
    int l = 0, b = 0;
```
```
    double ar;
```
```
    public void input()
```
```
    {
```
```
        super.input();
```
```
        l = 6;
```
```
        b = 4;
```
```
    }
```
```
    public void area()
```
```
    {
```
```
        super.area();
```
```
        ar = l * b;
```

        System.out.println("Area of rectangle:"+ar);

```
    }
```
```
}
```
```
public class Demo
```
```
{
```

    public static void main(String[] args)

```
    {
```

        Rectangle obj = new Rectangle();

```
        obj.input();
```
```
        obj.area();
```
```
    }
```
```
}
```

Output:

$ javac Demo.java
$ java  Demo
 
Area of circle:78.5
Area of rectangle:24.0

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