In Java, an interface is a blueprint of a class that defines a set of methods (without implementation) that a class must implement. It is used to achieve abstraction and define a contract between different classes.
To create an interface in Java, follow these steps:
-
Start by creating a new Java file with a
.java
extension and give it a meaningful name. For example,MyInterface.java
. -
Declare the interface using the
interface
keyword followed by the name of the interface. For example:public interface MyInterface { }
-
Inside the interface, define the methods that the implementing classes must override. The methods should be declared without a body, ending with a semicolon. For example:
public interface MyInterface { void method1(); int method2(String param); }
You can define any number of methods in an interface. These methods act as a contract for the implementing classes, ensuring that they provide the necessary functionality.
-
Optionally, you can also define constants in an interface. Constants are declared using the
final
andstatic
keywords. For example:public interface MyInterface { int MAX_SIZE = 10; String DEFAULT_COLOR = "red"; }
Constants declared in an interface are effectively
public
,static
, andfinal
. They can be accessed directly from the interface or any implementing class. -
Save the interface file and use it in your Java programs. To implement an interface in a class, use the
implements
keyword followed by the interface name. For example:public class MyClass implements MyInterface { // Implement the methods of MyInterface here }
The implementing class must provide an implementation (method body) for all the methods defined in the interface. Failure to do so will result in a compilation error.
Conclusion
Interfaces in Java provide a way to achieve abstraction and define contracts between classes. By creating interfaces, you can enforce a standard behavior across different classes.