Java: Keep binary file blob in memory for multiple uses (byte[]? ByteBuffer? ...?)

Question

I read binary files from an InputStream and have to keep them in memory for further processing. The most obvious approach is to keep the read data of each file in a byte[] array. But I guess there are more elegant ways that provide some OO API around "file blobs" in memory. What would you recommend?

• Multiple reads must be possible without having to rebuild the data structure (read access mustn't affect internal state of the file blob)
• (Random) Write access not required. No need to modify certain bytes
• Finally, after having been inspected by multiple visitors, the file blob kept in memory will be written to disk
• Pure Java 8 only, no third-party libs like Apache Commons, Guava etc.

Answer 1

If everything fits into memory and the data is discarded quickly, use a byte[]s or non-direct (!) java.nio.ByteBuffers (which are just wrappers around byte arrays anyway). Byte buffers have the advantage that you can provide a reference to the same blob through which no changes to the blob can be made, using the asReadOnlyBuffer() method. With byte[], this requires a defensive copy. Regarding the additional overhead from ByteBuffer: The Hotspot compilers are pretty good at eliminating that, and your blobs seem to be fairly large, so the additional allocation should not matter.