Java.util.zip: putNextEntry

Question

I am trying to modify a file in a zip file using java.util.net Since it is not possible to directly modify the file, and I want to change only one file, I simply create a new zip file containing mainly the contents of the template and replace the specific file with at least this plan.

Here are the most important lines of my attempt:

Enumeration<? extends ZipEntry> entries = zif.entries();
while (entries.hasMoreElements()) {
ZipEntry currentEntry = entries.nextElement();
if (!currentEntry.isDirectory() && currentEntry.getSize() >0 && currentEntry.getCompressedSize() > 0)
{
    System.out.println(currentEntry.getName() + ": " + currentEntry.getSize() + "-" + currentEntry.getMethod());
    if (currentEntry.getName() != "file_i_want_to_change")
    {
        try {
            this.zos.putNextEntry(currentEntry);  // HERE the exception is thrown
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println(e.getMessage());
        }
    }
}

Information: zif = ZipFile, correctly initialized and opened from an existing file; zos = ZipOutputStream correctly initialized for the new file.

This is an exception:

java.util.zip.ZipException: invalid entry size (expected 39 but got 0 bytes)
at java.util.zip.ZipOutputStream.closeEntry(ZipOutputStream.java:228)
at java.util.zip.ZipOutputStream.putNextEntry(ZipOutputStream.java:144)
at TestClass.replace(TestClass.java:117)
at TestClass.main(TestClass.java:10)

whereas TestClass: 117 is a comment line in which it does not work.

The funny thing is that System.out.println in a piece of code works fine and without messages about files of size 0.

Does anyone see a mistake I could make?

Any idea is welcome.

Thanks in advance and best wishes.

Answer 1

ZipEntry , .

        this.zos.putNextEntry(new ZipEntry(currentEntry));
        int len;
        while ((len = zis.read(buf)) >= 0)
        {
           zos.write(buf, 0, len);
        }