Java 8 Applying stream filter based on a condition

One way to do it is

Stream<Source> stream = sourceMeta.getAllSources.parallelStream().map(x -> (Source)x);
if(isAccessDisplayEnabled) stream = stream.filter(s -> isAccessDisplayEnabled(s));
src = stream.filter(s - > containsAll(s, substrings, searchString))
            .collect(Collectors.toList());

another

 src = sourceMeta.getAllSources.parallelStream().map(x -> (Source)x)
     .filter(isAccessDisplayEnabled? s - > isAccessDisplayEnabled(s): s -> true)
     .filter(s - > containsAll(s, substrings, searchString))
     .collect(Collectors.toList());

In either case, note how performing one type cast at the beginning simplifies the entire stream pipline.

Both solutions avoid re-evaluating isAccessDisplayEnabled for every stream element, however, the second relies on the JVM’s capability of inlining s -> true when this code turns out to be performance critical.