what is the difference between implementing from an interface and extending from the object class?

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I'm new to java, I hope this question isn't too basic. I'm having trouble understanding why interfaces are needed, and what the difference is between implementing and inheriting.

If I would want to use the Comparable method in my program,(java.lang.Comparable) why can't I just make my class inherit from Comparable?

public class Main {

    public static void main(String[] args) {

    class DocumentReader extends Comparable;

Why does IntelliJ say 'no interface expected here'?

Loosely speaking, and not entirely accurate since JDK 8... but ok for grasping the basics.

An interface is a specification of methods that a class implementing the interface must have. The interface provides no implementation. Thus, saying your class 'implements Comparable' places an obligation on it to provide a compareTo method with a particular signature.

A class may contain actual method implementations, and perhaps member data. Extending a class is essentially a specialization of that class. You get everything the base class does, which you can perhaps modify (by overriding base methods) or augment (by adding new methods).


EXCEPT that there are such things as abstract methods, where the base class provides no implementation, and thus forces the extending class to provide an implementation.

From one point of view, then, you could regard an interface as an abstract class in which all methods are abstract. This would be workable, except that Java only allows a class to extend one class (no 'class X extends A, B'), but a class can implement more than one interface ('class X implements A, B' - my syntax might not be exact). There's a technical reason for the restriction on inheriting from multiple classes, but I'll skip that here.

As I remarked at the start, this is not entirely true as of JDK 8 - there are 'default methods' in interfaces, so the line gets a little blurry.

I'd regard an interface as like a specification for the kind of plugs and sockets an object must provide if it's to be connected to other objects in standard ways. You want your objects to be 'compared' so they can be arranged in order by other components? Then you must implement Comparable.

What is the difference between implementing an interface and , Though both are an integral part of application development using the object- oriented methodology, an interface is more abstract than class� The main difference between extends and implements in Java is that the keyword “extends” helps to use properties and methods of a superclass while the keyword “implements” allows a class to implement an interface. Java is a high level, general purpose programming language developed by James Gosling.

i am trying to explain programmatically. Extends : When you want to extend a subclass to be extended in inheritance that we use Java extends. Implements: When an implement an interface, we use the keyword implement.

Extend vs Implements : In short, extends is for extending a class and implements are for implementing an interface.

As Java doesn’t support multiple inheritances and this problem overcomes by multiple interfaces.

Extends:

class Person
  {
     String name;
     Person(String n)
      {
        name = "Person:  " + n;
      }
   }
class Mother extends Person
  {
     Mother(String n)
     {
       super(n);
       name = "Mother:  " + n;
     }
  void FeedChildren()
    {
       System.out.println(name + " is feeding the kids ...");
    }
 }
class Wife extends Person
  {
    Wife(String n)
     {
         super(n);
         name = "Wife:  " + n;
      }
  void CallHusband()
   {
      System.out.println(name + " is calling the husband ...");
   }
}
public class Test
  {
      public static void main(String args[])
        {
            Person p = new Person("Prerna");
            Mother m = new Mother("Mahima");
            Wife w = new Wife("Raani");
            System.out.println("p is a " + p.name);
            System.out.println("m is a " + m.name);
            System.out.println("w is a " + w.name);
            m.FeedChildren();
            w.CallHusband();
        }
  }

Here the base class is Person, Mother, and Wife but when Wife and Mother are same the same person and that is the person we are talking about.

Implements

class Person
  {
    String name;
    Person(String n)
    {
      name = "Person:  " + n;
    }
 }
interface Mother
  {
    public void FeedChildren();
  }
interface Wife
  {
    public void CallHusband();
  }
class WifeAndMother extends Person implements Wife, Mother
  {
    WifeAndMother(String n)
     {
        super(n);
        name = "Wife and mother:  " + n;
     }
public void FeedChildren()
   {
       System.out.println(name + " is feeding the children.");
   }
public void CallHusband()
  {
      System.out.println(name + " is calling her husband.");
  }
}
public class Test
 {
    public static void main(String args[])
      {
          Person p = new Person("Prerna");
          WifeAndMother w = new WifeAndMother("Raani");
          System.out.println("p is a " + p.name);
          System.out.println("w is a " + w.name);
          w.FeedChildren();
          w.CallHusband();
      }
  }

Difference between extends and implements , [Solved] What is the difference between “extends” and “implements” in Java? Likewise, a class "implements" an interface because the interface merely defines Object ) is automatically a base class to every Java class. In case of implementing Runnable interface: You create 1 Task class object and 20 Thread class objects resulting size = 1*100k+ 20*10K = 100k+200k = 300K. So, for the same requirement, in case of extending “Thread” class, the total memory size is 2000k, whereas, in implementing Runnable interface, it is 300K.

You can only extend from one class and implement multiple interfaces.

[Solved] What is the difference between “extends” and “implements , In Java, extends is used for extending a class and implements is used for implementing the interfaces. It's main difference between extends vs implements. Home / Java / Java Object Oriented Programming / Java extends vs implements keywords To implement an interface, class must use implements keyword. In Java� A class describes the attributes and behaviors of an object. An interface contains behaviors that a class implements. A class may contain abstract methods, concrete methods. An interface contains only abstract methods. Members of a class can be public, private, protected or default.

Java extends vs implements keywords, Thus if a variable has a type given by an interface, then any object from a class implementing that interface can be assigned to that variable. If a formal parameter's� The significant differences between extending Thread class and implementing Runnable interface: When we extend Thread class, we can’t extend any other class even we require and When we implement Runnable, we can save a space for our class to extend any other class in future or now. When we extend Thread class, each of our thread creates

Lecture 28 -- Difference between extends and implements, Inheritance is an important pillar of OOP(Object Oriented Programming). In this article, the difference between extends and implements is discussed. An interface is a special type of class which implements a complete� Implement/Extend: A class can implement any number of interface and can extend only one class. An interface can extend multiple interfaces but can not implement any interface. Constructor : A class can have constructors to initialize the variables. An interface can never have a constructor as there is hardly any variable to initialize.

Extends vs Implements in Java, As Java doesn't support multiple inheritances and this problem overcomes by multiple interfaces. Do you know the Difference Between Abstract Class and� With interfaces, a class gains behavior from the interface it implements. (this is the one I chose) With inheritance, a class must implement the methods defined by its superclass. With interfaces, a class gains both instance variables and behaviors from the interface it implements.