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How to create our own/custom functional interface in Java?
The functional interface is a simple interface with only one abstract method. A lambda expression can be used through a functional interface in Java 8. We can declare our own/custom functional interface by defining the Single Abstract Method (SAM) in an interface.
Syntax
interface CustomInterface {
// abtstact method
}Example
@FunctionalInterface
interface CustomFunctionalInterface {
void display();
}
public class FunctionInterfaceLambdaTest {
public static void main(String args[]) {
// Using Anonymous inner class
CustomFunctionalInterface test1 = new CustomFunctionalInterface() {
public void display() {
System.out.println("Display using Anonymous inner class");
}
};
test1.display();
// Using Lambda Expression
CustomFunctionalInterface test2 = () -> { // lambda expression
System.out.println("Display using Lambda Expression");
};
test2.display();
}
}Output
Display using Anonymous inner class Display using Lambda Expression
Updated on: 14-Jul-2020
9K+ Views
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