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Update index.md (#26358) 

* Update index.md

Added statements to visualize interfaces differently.

* Formatting changes
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Raymart Evangelista 2018-12-26 15:26:34 -08:00 committed by Manish Giri
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@ -3,7 +3,11 @@ title: Interfaces
---
# Interfaces
Interface in Java is a bit like the Class, but with a significant difference : an `interface` can _only_ have method signatures, fields and default methods. Since Java 8, you can also create [default methods](https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html). In the next block you can see an example of interface :
Interface in Java is a bit like the Class, but with a significant difference : an `interface` can _only_ have method signatures, fields and default methods. Since Java 8, you can also create [default methods](https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html).
Classes that implement an interface are thought to be signing a contract and agreeing to perform the specific behaviors listed in the interface. If the classes that implement an interface do not implement all the methods of the interface, then such a class needs to be defined as `abstract`.
In the next block you can see an example of interface :
```java
public interface Vehicle {
@ -46,7 +50,7 @@ Vehicle tesla = new Car();
tesla.start(); // starting engine ...
```
An Interface **can not** contain a constructor methods,therefore,you **can not** create an instance of an Interface itself. You must create an instance of some class implementing an Interface to reference it. Think of interfaces as a blank contract form, or a template.
An Interface **can not** contain a constructor methods,therefore,you **can not** create an instance of an Interface itself. You must create an instance of some class implementing an Interface to reference it. Think of interfaces as a blank contract form, or a template.
What can you do with this feature? Polymorphism! You can use only interfaces to refer to object instances!