Pipe or Swap Input / Output Streams in Java

A list of analyser classes which analyse a InputStream for dependencies, changes a few things and write it to an OutputStream:

public Set<Dependency> analyse(InputStream i, OutputS开发者_C百科tream o);

The analysers should be chained like:

for(DocumentAnalyser analyser : a) {
 o.getDependencies().addAll(analyser.analyse(in, out));
 in = new ByteArrayInputStream(out.toByteArray());
} 

Now I'm working in a environment where in is final.

1. Is there a better way to "chain" the streams?
2. Is the "swap" operation from "out" to "in" with ByteArrayInputStream expensive?
3. How to deal with the problem that "in" is final?

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1. Use helper threads and java.io.PipedInputStream/java.io.PipedOutputStream pairs.
2. Probably it will not perform well on big streams.
3. As it is said in another response, use a local non-final variable to do the chaining

Note that by applying 1. you do not need to worry about 2 because you are in fact piping the streams.

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For question 2.
I would provide my own subclass that has a direct access to ByteArrayInputStream's and ByteArrayOutputStream's buffer. That way you don't waist memory and time by making extra copy in toByteArray.

For question 3.
Assign it to a local non-final variable,

InputStream nonFinalIn = in;
for(DocumentAnalyser analyser : a) {
 o.getDependencies().addAll(analyser.analyse(nonFinalIn, out));
 nonFinalIn = new ByteArrayInputStream(out.toByteArray());
}

Beware, though, that the original in will no longer be valid ( it will be at the end-of-stream )