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How to implement Function interface with lambda expression in Java?
Function<T, R> interface is a functional interface from java.util.function package. This interface expects one argument as input and produces a result. Function<T, R> interface can be used as an assignment target for a lambda expression or method reference. It contains one abstract method: apply(), two default methods: andThen() and compose() and one static method: identity().
Syntax
@FunctionalInterface public interface Function<T, R> { R apply(T t); }
Example
import java.util.function.Function; public class FunctionTest { public static void main(String[] args) { Function<Integer, Integer> f1 = i -> i*4; // lambda System.out.println(f1.apply(3)); Function<Integer, Integer> f2 = i -> i+4; // lambda System.out.println(f2.apply(3)); Function<String, Integer> f3 = s -> s.length(); // lambda System.out.println(f3.apply("Adithya")); System.out.println(f2.compose(f1).apply(3)); System.out.println(f2.andThen(f1).apply(3)); System.out.println(Function.identity().apply(10)); System.out.println(Function.identity().apply("Adithya")); } }
Output
12 7 7 16 28 10 Adithya
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