Java Tutorials
Java 8 introduced Lambda Expressions, These expressions depends on Functional Interfaces. A Functional Interface is an Interface which has only one Abstract method, and also it can have static and default methods. It can optionally be decorated with @FunctionalInterface Annotation.
Earlier java(i.e befor JDK8) , an interfaces can be implemented using class/anonymous class. An anonymous class is a class which has no class name, and can implement interface methods.
for ex: implementing interface as an Anonymous class.
interface IA
{
int add ( int a, int b );
}
public class TestImpl {
IA obj = new IA(){
@override
int add ( int a, int a )
{
return a + b;
}
};
public static void main(String[] args)
{
System.out.println("
Interface implementation using Anonymous Class");
TestImpl impl = new TestImpl ();
int result = impl.obj.add( 10 , 20 );
System.out.println("Calling interface
add method : "+ result);
}
}
//creating Anonymous method, assiging it to functional interface IA
IA anyonymous = ( a , b ) -> a + b;
//Invoking Anonymous method
int result = anonymous.add( 10, 20 );
System.out.println("Calling interface add method using Lambda Expression : "+ result);
Java 8 provides many built-in Functional Interfaces. These interfaces located in java.util.function package
BiConsumer BiFunction BiPredicate BinaryOperator BooleanSupplier Consumer DoubleBinaryOperator DoubleConsumer DoubleFunction DoublePredicate DoubleSupplier DoubleToIntFunction DoubleToLongFunction DoubleUnaryOperator Function IntBinaryOperator IntConsumer IntFunction IntPredicate IntSupplier IntToDoubleFunction IntToLongFunction IntUnaryOperator LongBinaryOperator LongConsumer LongFunction LongPredicate LongSupplier LongToDoubleFunction LongToIntFunction LongUnaryOperator ObjDoubleConsumer ObjIntConsumer ObjLongConsumer Predicate Supplier ToDoubleBiFunction ToDoubleFunction ToIntBiFunction ToIntFunction ToLongBiFunction ToLongFunction UnaryOperator
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