Method References
Functional interface instances can be directly created from methods and
constructors.
Since Java 8
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.IntFunction;
import java.util.function.Supplier;
public class MethodReferences {
static class Foo {
Foo() {
System.out.println("constructor");
}
void instanceMethod() {
System.out.println("instanceMethod");
}
void instanceMethod(String parameter) {
System.out.println("instanceMethod " + parameter);
}
static void classMethod() {
System.out.println("classMethod");
}
}
public static void main(String[] args) {
// Constructor as reference
Supplier<Foo> supplier = Foo::new;
Foo foo = supplier.get();
// Bound instance method as reference
Runnable runnable = foo::instanceMethod;
runnable.run();
// Unbound instance method as reference
Consumer<Foo> consumer = Foo::instanceMethod;
consumer.accept(foo);
// Unbound instance method with parameter as reference
BiConsumer<Foo, String> biconsumer = Foo::instanceMethod;
biconsumer.accept(foo, "hello");
// Class method as reference
Runnable runnable2 = Foo::classMethod;
runnable2.run();
// Array constructor as reference
IntFunction<Foo[]> function = Foo[]::new;
Foo[] array = function.apply(42);
System.out.println(array.length);
}
}
This snippet at GitHub
