InterviewSolution
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InterviewSolution
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What are functional or SAM interfaces? |
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Answer» Functional Interfaces are an interface with only one ABSTRACT method. Due to which it is also known as the Single Abstract Method (SAM) interface. It is known as a functional interface because it wraps a function as an interface or in other words a function is represented by a single abstract method of the interface. Functional interfaces can have any NUMBER of default, static, and overridden METHODS. For declaring Functional Interfaces @FunctionalInterface annotation is optional to use. If this annotation is used for interfaces with more than one abstract method, it will generate a compiler error. @FunctionalInterface // Annotation is optional public interface Foo() { // Default Method - Optional can be 0 or more public default STRING HelloWorld() { return "Hello World"; } // Static Method - Optional can be 0 or more public static String CustomMessage(String msg) { return msg; } // Single Abstract Method public void bar(); } public class FooImplementation implements Foo { // Default Method - Optional to Override@Overridepublic default String HelloWorld() { return "Hello Java 8"; } // Method Override@Overridepublic void bar() { System.out.println(“Hello World”);} } public static void main(String[] args) { FooImplementation fi = new FooImplementation();System.out.println(fi.HelloWorld());System.out.println(fi.CustomMessage(“Hi”));fi.bar();} |
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