package es.sandbox.spikes.java8.interfaces;

/**
 * Created by jeslopalo on 30/12/15.
 */
@java.lang.FunctionalInterface
public interface SimpleFunctionalInterface {

    void doWork();
}

package es.sandbox.spikes.java8.interfaces;

/**
 * Created by jeslopalo on 30/12/15.
 */
@FunctionalInterface
public interface SimpleFunctionalInterface {

    void doWork();
}

Add import to FunctionalInterface