how to write lambda expression for the abstract class

Question

I have abstract class which have two methods as follows:

public abstract class SessionExecutionBody {
   public Object execute() {
     executeWithoutResult();
     return null;
   }

   public void executeWithoutResult() {}
} 

and I implement the class as follows:

final HTTPDestination destination = sessionService.executeInLocalView(new SessionExecutionBody() {
            @Override
            public Object execute() {
                userService.setCurrentUser(userService.getAdminUser());
                final String destinationName = getConfigurationService().getConfiguration().getString(DESTINATION_PROPERTY);
                return getHttpDestinationService().getHTTPDestination(destinationName);

When I run sonarLint its showing major issue convert this anonymous class to lambda expression but I am unable to find the way to right the same , Can I convert that expression into a lambda?

Answer 1

I'm afraid you can't. That is not a functional interface with one abstract method to implement it in the lambda style.

Can I convert that expression into a lambda?

You could if you make the following changes:

@FunctionalInterface // to guarantee the next rule
interface SessionExecutionBody {
    Object execute(); // has exactly one abstract method

    default void executeWithoutResult() {} // other methods should be default/static
}
...
sessionService.executeInLocalView(() -> { /* a body */ return ...; })