StackOverflow2013

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POjava.util.zip - ZipInputStream v.s. ZipFile
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copied!<p>I have some general questions regarding the <code>java.util.zip</code> library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.:</p> <pre><code><component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> </code></pre> <p><em>Please note that the order of the components during import is relevant.</em></p> <p>Now every component should occupy its own file which should be <em>externally</em> versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions:</p> <p>Q1. May the <code>ZipInputStream</code> guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses <code>ZipOutputStream</code>? I assume reading is something like:</p> <pre><code> ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } </code></pre> <p>I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind.</p> <p>Q2. If I use <code>ZipFile</code> (which I prefer) what is the performance impact of calling <code>getInputStream()</code> hundreds of times? Will it be much slower than the <code>ZipInputStream</code> solution? The zip is opened only once and <code>ZipFile</code> is backed by <code>RandomAccessFile</code> - is this correct? I assume reading is something like:</p> <pre><code> ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } </code></pre> <p>Q3. Are the input streams retrieved from the same <code>ZipFile</code> thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties?</p> <p>Thanks for your answers!</p>

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