List .zip directories without extracting

I suggest you have a look at ZipFile.entries().

Here’s some code:

try (ZipFile zipFile = new ZipFile("test.zip")) {
    Enumeration<? extends ZipEntry> zipEntries = zipFile.entries();
    while (zipEntries.hasMoreElements()) {
        String fileName = zipEntries.nextElement().getName();
        System.out.println(fileName);
    }
}

If you’re using Java 8, you can avoid the use of the almost deprecated Enumeration class using ZipFile::stream as follows:

zipFile.stream()
       .map(ZipEntry::getName)
       .forEach(System.out::println);

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If you need to know whether an entry is a directory or not, you could use ZipEntry.isDirectory. You can’t get much more information than than without extracting the file (for obvious reasons).

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If you want to avoid extracting all files, you can extract one file at a time using ZipFile.getInputStream for each ZipEntry. (Note that you don’t need to store the unpacked data on disk, you can just read the input stream and discard the bytes as you go.