PlayingWithStreams.java

  public void shortListProgramsAndWorkflows(List<Program> programs, List<ProgramWorkflow> workflows) {
		Predicate<Entry<ProgramWorkflow, Program>> predicate = entry -> {
			return entry.getValue().getAllWorkflows().contains(entry.getKey());
		};
		filter(programs, workflows, predicate);
	}
	
	public void shortListWorkflowsAndStates(List<ProgramWorkflow> workflows, List<ProgramWorkflowState> states) {
		Predicate<Entry<ProgramWorkflowState, ProgramWorkflow>> predicate = entry -> {
			return entry.getValue().getStates(false).contains(entry.getKey());
		};
		filter(workflows, states, predicate);
	}
	
	public void shortListProgramsAndStates(List<Program> programs, List<ProgramWorkflowState> states) {
		Predicate<Entry<ProgramWorkflowState, Program>> predicate = entry -> {
			for (ProgramWorkflow workflow : entry.getValue().getAllWorkflows()) {
				if (workflow.getStates(false).contains(entry.getKey())) {
					return true;
				}
			}
			return false;
		};
		filter(programs, states, predicate);
	}
	
	private <Owner, Owned> void filter(List<Owner> owningTypes, List<Owned> ownedTypes, Predicate<Entry<Owned, Owner>> predicate) {	
	    List<Entry<Owned, Owner>> ownedToOwnersMap = new ArrayList<>();
	    List<Owner> ownersFiltrate = new ArrayList<>();
	    List<Owned> ownedMembersFiltrate = new ArrayList<>();
	  
	    Function<Owner, List<Entry<Owned, Owner>>> ownersToOwnedMapper = owner -> {
		    HashMap<Owned, Owner> map = new HashMap<>();
		    for (Owned ownedType : ownedTypes) {
			     map.put(ownedType, owner);
		    }
		    return new ArrayList<>(map.entrySet());
	    };
	  
	    Consumer<Entry<Owned, Owner>> updateFiltrates = entry -> {
		   ownedMembersFiltrate.add(((Entry<Owned, Owner>)entry).getKey());
		   ownersFiltrate.add(((Entry<Owned, Owner>)entry).getValue());

	    };
	  
	    owningTypes.stream().map(ownersToOwnedMapper).forEach(item -> ownedToOwnersMap.addAll(item));
	    ownedToOwnersMap.stream().filter(predicate).forEach(updateFiltrates);
	  
	    // update the shortlists
	    owningTypes.retainAll(ownersFiltrate);
	    ownedTypes.retainAll(ownedMembersFiltrate);
	}