public class Main { public static void main(String[] args) { ChildInterface def = (s) -> { System.out.println("lambda: " + s); }; def.doIt(); def.likeIt("I like the IExtended.."); } } interface ChildInterface extends ParentInterface { public default void doIt() { System.out.println("my extended doIt function.."); } } interface ParentInterface { public void likeIt(String s); public default void doIt() { System.out.println("doIt function.."); } }