ExecutionFlow.java

import java.util.List;
import static java.util.stream.Collectors.toList;

 class Command {
 }

interface CommandHandler {
	public Result handle(Command cmd);
}

enum Result {
	  OK,KO;
}

class DomainHandler implements CommandHandler {

	@Override
	public Result handle(Command cmd) {
		//try{
    return Result.OK;
    //}catch(Exception exc){
    // return Result.KO;
    //}
	}

}

public class ExecutionFlow {

	public static void main(String[] args) {
		
		List<Command> cmds = List.of(new Command(),new Command(),new Command());
		DomainHandler handler = new DomainHandler();
		
        // managing void return type
		cmds.stream().forEach(handler::handle);
		
		// using a placeholder return type
		List<Result> collect = cmds.stream().map(handler::handle).collect(toList());
		
	}
}