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How to use wildcards in filenames when reading in files

I'm working on an application that will read in SystemOut.Log files and process them. Sometimes archived files may be named slightly differently, such as SystemOut_10:20_09/07/2021-10:45_09/07/2021.Log. It's always of the form SystemOut(Some more text here).Log.
I had a little read up and stumbled across wildcards and came to the conclusion that if I were to pass SystemOut*.Log into my application as the filename it would work. But I was wrong.
I originally get my filename through a properties file like so.
fileName=prop.getProperty("fileName");
I then just tried to concatenate *.Log on the end.
fileName=fileName+"*.Log";
When I print out fileName it is "SystemOut*.Log" but when I pass in this filename to my method that reads files it doesn't work as no file is found with that name.
Am I making an error in the code or have I just misunderstood how wildcards work? Thanks

Try FileUtils from Apache commons-io (listFiles and iterateFiles methods):
The code you need is
File dir = new File(".");
FileFilter fileFilter = new WildcardFileFilter("*.Log");
File[] files = dir.listFiles(fileFilter);
for (int i = 0; i < files.length; i++) {
System.out.println(files[i]);
}

Read the data from TXT file inside Zip File without extracting the contents in Matlab

I have tab delimited ascii data in txt files which are zip compressed (and the zip may or may not contain other files). I would like to read this data into a matrix without uncompressing the zip files.
There were a few similar #matlab / #java posts earlier:
Read the data of CSV file inside Zip File without extracting the contents in Matlab
Extracting specific file from zip in matlab
Read Content from Files which are inside Zip file
I have gotten this far thanks to the above - I can identify the .txt inside the zip, but don't know how to actually read its contents. First example:
zipFilename = 'example.zip';
zipJavaFile = java.io.File(zipFilename);
zipFile=org.apache.tools.zip.ZipFile(zipJavaFile);
entries=zipFile.getEntries;
cnt=1;
while entries.hasMoreElements
tempObj=entries.nextElement;
file{cnt,1}=tempObj.getName.toCharArray';
cnt=cnt+1;
end
ind=regexp(file,'$*.xml$');
ind=find(~cellfun(#isempty,ind));
file=file(ind);
file = cellfun(#(x) fullfile('.',x),file,'UniformOutput',false);
% Now Operate Any thing on File.
zipFile.close
HOWEVER, I found no example as to how to "operate anything on file". I can extract the path within the zip file, but don't know how to actually read the contents of this txt file. (I wish to directly read its contents into memory -- a matrix --, without extraction, if possible.)
The other example is
zipFilename = 'example.zip';
zipFile = org.apache.tools.zip.ZipFile(zipFilename);
entries = zipFile.getEntries;
while entries.hasMoreElements
entry = entries.nextElement;
entryName = char(entry.getName);
[~,~,ext] = fileparts(entryName);
if strcmp(ext,'.txt')
inputStream = zipFile.getInputStream(entry);
%Read the contents of the file
inputStream.close;
end
end
zipFile.close
The original example contained code to extract the file, but I merely want to read it directly into memory. Again, I don't know how exactly to work with this inputStream.
Could anyone give me a suggestion with a MWE?

It might be a little late, but maybe someone can use it:
(the code was tested in Matlab R2018a)
zipFilename = 'example.zip';
zipFile = org.apache.tools.zip.ZipFile(zipFilename);
entries = zipFile.getEntries;
while entries.hasMoreElements
entry = entries.nextElement;
entryName = char(entry.getName);
[~,~,ext] = fileparts(entryName);
if strcmp(ext,'.txt')
inputStream = zipFile.getInputStream(entry);
%Read the contents of the file
buffer = java.io.ByteArrayOutputStream();
org.apache.commons.io.IOUtils.copy(inputStream, buffer);
data = char(typecast(buffer.toByteArray(), 'uint8')');
inputStream.close;
end
end
zipFile.close

Replace specific file inside Zip archive without extracting the whole archive in Java

I'm trying to get a specific file inside a Zip Archive, extract it, Encrypt it, and then get it back inside the archive replacing the origial one.
here's what I've tried so far..
public static boolean encryptXML(File ZipArchive, String key) throws ZipException, IOException, Exception {
ZipFile zipFile = new ZipFile(ZipArchive);
List<FileHeader> fileHeaderList = zipFile.getFileHeaders();
for (FileHeader fh : fileHeaderList)
{
if (fh.getFileName().equals("META-INF/file.xml"))
{
Path tempdir = Files.createTempDirectory("Temp");
zipFile.extractFile(fh, tempdir.toString());
File XMLFile = new File(tempdir.toFile(), fh.getFileName());
// Encrypting XMLFile, Ignore this part
// Here, Replace the original XMLFile inside ZipArchive with the encrypted one <<<<<<<<
return true;
}
}
return false;
}
I stuck at the replacing part of the code is there anyway I can do this without having to extract the whole Zip Archive?
Any help is appreciated, thanks in advance.

Not sure if this will help you as you are using a different library but the solution in ZT Zip would be the following.
ZipUtil.unpackEntry(new File("/tmp/demo.zip"), "foo.txt", new File("foo.txt"));
// encrypt the foo.txt
ZipUtil.replaceEntry(new File("/tmp/demo.zip"), "foo.txt", new File("foo.txt"));
This will unpack the foo.txt file and then after you encrypt it you can replace the previous entry with the new one.

You may use the ZipFilesystem (as of Java 7) as explained in the Oracle documentation to read/write within a zip file as if it were its own file system.
However, on my machine, this unpacks and re-packs the zip file under the hood anyway (tested with 7 and 8). I am not sure if there is a way to reliably change zip files like you describe.

Bingo!
I'm able to do it that way
ZipParameters parameters = new ZipParameters();
parameters.setIncludeRootFolder(true);
zipFile.removeFile(fh);
zipFile.addFolder(new File(tempdir.toFile(), "META-INF"), parameters);

how to check if a ZIP file is empty in Java?

I have the following piece of code -
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
ZipOutputStream zos = new ZipOutputStream(outputStream);
for (int i = 0; i < params.getGrades().size(); i++) {
generateReport(param1, param2, zos);
}
zos.flush();
zos.close();
In the generateReport method, I have code to generate my reports as xls files and add them to ZIP.
Is there any way we can check if any files have been written in the ZIP file, or if the ZIP file is empty? is there any property I can use?
Thanks,
Raaz

You can use the ZipFile from the java.util.zip package.
You can invoke the
size()
method.

After you close zos, outputStream.size() gives you the number of bytes written. You would have to allow for whatever the ZIP header size is for an empty ZIP file.

See:
http://www.java-examples.com/get-number-entries-zip-file-example
and:
Count files in ZIP's directory - JAVA, Android
and:
Android: Get Number of Files within Zip?

#Raaz, Please go through this link.
In that you can see a Class called 'ZipEntry'. It represents the files contained in a zip folder. It provides some useful methods such as:
zipEntry.getName(); // name of the file contained by zip.
zipEntry.getSize(); // size of the file contained by zip.

#Didier - I decided to take your advice on returning a value, but ended up doing it this way -
Instead of checking if a file has been added to the ZIP, I checked if the list data I'm trying to write in an xls file (the file which in turn gets added to the ZIP) is empty. If it's empty, then I set a error value to "No file generated". If the list is not empty, I assigned the an empty value to the string and returned it to the calling function.

Reading files from an embedded ZIP archive

I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length.
Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file.
For performance reasons, I cannot copy the ZIP achive into a separate file before opening it.
edit: Just to be clear, I do have random access to the file.

I've come up with a quick hack (which needs to get sanitized here and there), but it reads the contents of files from a ZIP archive which is embedded inside a TAR. It uses Java6, FileInputStream, ZipEntry and ZipInputStream. 'Works on my local machine':
final FileInputStream ins = new FileInputStream("archive.tar");
// Zip starts at 0x1f6400, size is not needed
long toSkip = 0x1f6400;
// Safe skipping
while(toSkip > 0)
toSkip -= ins.skip(toSkip);
final ZipInputStream zipin = new ZipInputStream(ins);
ZipEntry ze;
while((ze = zipin.getNextEntry()) != null)
{
final byte[] content = new byte[(int)ze.getSize()];
int offset = 0;
while(offset < content.length)
{
final int read = zipin.read(content, offset, content.length - offset);
if(read == -1)
break;
offset += read;
}
// DEBUG: print out ZIP entry name and filesize
System.out.println(ze + ": " + offset);
}
zipin.close();

1.create FileInputStream fis=new FileInputStream(..);
position it at the start of embedded zipfile:
fis.skip(offset);
open ZipInputStream(fis)

I suggest using TrueZIP, it provides file system access to many kinds of archives. It worked well for me in the past.

If you're using Java SE 7, it provides a zip fie system which allows you to read/ write files in the zip directly: http://docs.oracle.com/javase/7/docs/technotes/guides/io/fsp/zipfilesystemprovider.html

I think apache commons compress may help you.
There is a class org.apache.commons.compress.archivers.zip.ZipArchiveEntry, which inherit java.util.zip.ZipEntry.
It has a method getDataOffset(), that can get the offset of data stream within the archive file.

7-zip-JavaBinding is a Java wrapper for the 7-zip C++ library.
The code snippets page in particular has some nice examples including printing a list of items in an archive, extracting a single file and opening multi-part archives.

Check whether zip4j helps you or not.
You can try PartInputStream to read zip file as per your use case.
I think it is better to create temp zip file and then accessing it.