hollow/src/main/java/com/netflix/hollow/core/util/StateEngineRoundTripper.java
public static void roundTripDelta(HollowWriteStateEngine writeEngine, HollowReadStateEngine readEngine) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        HollowBlobWriter writer = new HollowBlobWriter(writeEngine);
        writer.writeDelta(baos);
        HollowBlobReader reader = new HollowBlobReader(readEngine);
        reader.applyDelta(new ByteArrayInputStream(baos.toByteArray()));
        writeEngine.prepareForNextCycle();
    }
public static void roundTripDelta(HollowWriteStateEngine writeEngine, HollowReadStateEngine readEngine) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        HollowBlobWriter writer = new HollowBlobWriter(writeEngine);
        writer.writeDelta(baos);
        HollowBlobReader reader = new HollowBlobReader(readEngine);
        reader.applyDelta(new ByteArrayInputStream(baos.toByteArray()));
        writeEngine.prepareForNextCycle();
    }
Update the provided {@link HollowReadStateEngine} with the new state currently available in the {@link HollowWriteStateEngine}.
<p>
It is assumed that the readEngine is currently populated with the prior state from the writeEngine.

@param writeEngine the write state engine
@param readEngine the read state engine
@throws IOException if the round trip from write to read state failed