Answer Posted / Bholendra Pratap Pandey

In Java, an Interface is a collection of abstract methods (methods without a body) and constant variables (variables whose values cannot be changed). It defines a set of rules that a class implementing the interface must follow. Here's an example of an interface:

```java
interface Shape {
double PI = 3.14;
void draw();
}
```

A class can implement an interface by providing a concrete implementation for its abstract methods:

```java
class Circle implements Shape {
private double radius;

public Circle(double radius) {
this.radius = radius;
}

public void draw() {
// draw code for circle goes here
}
}
```

An Abstract class, on the other hand, can contain both abstract and concrete methods. It provides a partial implementation of the rules and leaves some parts to be implemented by the subclass:

```java
abstract class Animal {
private String name;

public Animal(String name) {
this.name = name;
}

public abstract void makeSound();

public void introduce() {
System.out.println("My name is " + name);
}
}
```

In summary, an interface declares a contract that the implementing class must adhere to (methods and constants), while an abstract class can have both concrete and abstract methods to provide a base structure for its subclasses.

i want test pattern of zylog company and some examples also

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