Implements vs extends: When to use? What's the difference?

In Java, the extends keyword is used to inherit from a superclass, and the implements keyword is used to implement an interface.

Here are the key differences between the two:

• A class can only inherit from a single superclass using the extends keyword, but it can implement multiple interfaces.
• A class that extends a superclass inherits all of its methods and fields, while a class that implements an interface must implement all of the methods defined in the interface.

Here's an example of how you might use the extends and implements keywords in a Java class:

public class MyClass extends SuperClass implements Interface1, Interface2 {
  // class definition goes here
}

In this example, MyClass is extending the SuperClass and implementing both Interface1 and Interface2.

To decide whether to use extends or implements, consider the following:

• If you want to create a new class that is a modified version of an existing class, with additional methods and fields, you should use extends.
• If you want to create a new class that is compatible with a specific interface and has a specific set of methods, but you don't need to add any additional fields or methods, you should use implements.

Keep in mind that a class can only inherit from a single superclass, but it can implement multiple interfaces. So, if you need to inherit from multiple classes or create a class that is compatible with multiple interfaces, you can use both extends and implements in your class definition.