How to read file from ZIP using InputStream?

Below is a simple example on how to extract a ZIP File, you will need to check if the file is a directory. But this is the simplest.

The step you are missing is reading the input stream and writing the contents to a buffer which is written to an output stream.

// Expands the zip file passed as argument 1, into the
// directory provided in argument 2
public static void main(String args[]) throws Exception
{
    if(args.length != 2)
    {
        System.err.println("zipreader zipfile outputdir");
        return;
    }

    // create a buffer to improve copy performance later.
    byte[] buffer = new byte[2048];

    // open the zip file stream
    InputStream theFile = new FileInputStream(args[0]);
    ZipInputStream stream = new ZipInputStream(theFile);
    String outdir = args[1];

    try
    {

        // now iterate through each item in the stream. The get next
        // entry call will return a ZipEntry for each file in the
        // stream
        ZipEntry entry;
        while((entry = stream.getNextEntry())!=null)
        {
            String s = String.format("Entry: %s len %d added %TD",
                            entry.getName(), entry.getSize(),
                            new Date(entry.getTime()));
            System.out.println(s);

            // Once we get the entry from the stream, the stream is
            // positioned read to read the raw data, and we keep
            // reading until read returns 0 or less.
            String outpath = outdir + "/" + entry.getName();
            FileOutputStream output = null;
            try
            {
                output = new FileOutputStream(outpath);
                int len = 0;
                while ((len = stream.read(buffer)) > 0)
                {
                    output.write(buffer, 0, len);
                }
            }
            finally
            {
                // we must always close the output file
                if(output!=null) output.close();
            }
        }
    }
    finally
    {
        // we must always close the zip file.
        stream.close();
    }
}

Code excerpt came from the following site:

http://www.thecoderscorner.com/team-blog/java-and-jvm/12-reading-a-zip-file-from-java-using-zipinputstream#.U4RAxYamixR

The ZipInputStream is an InputStream by itself and delivers the contents of each entry after each call to getNextEntry(). Special care must be taken, not to close the stream from which the contents is read, since it is the same as the ZIP stream:

public void readZipStream(InputStream in) throws IOException {
    ZipInputStream zipIn = new ZipInputStream(in);
    ZipEntry entry;
    while ((entry = zipIn.getNextEntry()) != null) {
        System.out.println(entry.getName());
        readContents(zipIn);
        zipIn.closeEntry();
    }
}

private void readContents(InputStream contentsIn) throws IOException {
    byte contents[] = new byte[4096];
    int direct;
    while ((direct = contentsIn.read(contents, 0, contents.length)) >= 0) {
        System.out.println("Read " + direct + "bytes content.");
    }
}

When delegating reading contents to other logic, it can be necessary to wrap the ZipInputStream with a FilterInputStream to close only the entry instead of the whole stream as in:

public void readZipStream(InputStream in) throws IOException {
    ZipInputStream zipIn = new ZipInputStream(in);
    ZipEntry entry;
    while ((entry = zipIn.getNextEntry()) != null) {
        System.out.println(entry.getName());

        readContents(new FilterInputStream(zipIn) {
            @Override
            public void close() throws IOException {
                zipIn.closeEntry();
            }
        });
    }
}

Well, I've done this:

 zipStream = new ZipInputStream(channelSftp.get("Port_Increment_201405261400_2251.zip"));
 zipStream.getNextEntry();

 sc = new Scanner(zipStream);
 while (sc.hasNextLine()) {
     System.out.println(sc.nextLine());
 }

It helps me to read ZIP's content without writing to another file.