ZipInputStream doesn't populate the crc in the ZipEntry for uncompressed entries before reading the data. It does populate the crc for compressed entries.

The relevant logic is here: https://github.com/openjdk/jdk/blob/4890b74c048a1472b87687294c316ecfb324e4ba/src/java.base/share/classes/java/util/zip/ZipInputStream.java#L541-L551

When iterating over the entries with ZipFile, ZipFile#getCrc returns crcs for entries regardless of compression.



```
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class Z {
  public static void main(String[] args) throws IOException {
    try (ZipInputStream zis = new ZipInputStream(Files.newInputStream(Path.of(args[0])))) {
      while (true) {
        ZipEntry ze = zis.getNextEntry();
        if (ze == null) {
          break;
        }
        System.err.printf("before read %s %s\n", ze.getName(), ze.getCrc());
        var unused = zis.readAllBytes();
        System.err.printf("after read %s %s\n", ze.getName(), ze.getCrc());
      }
    }
  }
}
```

$ echo 'hello' > a.txt
$ jar cf j.jar a.txt
$ java Z.java j.jar
...
before read a.txt -1
after read a.txt 909783072

$ jar -0cf j.jar a.txt
$ java Z.java j.jar
...
before read a.txt 909783072
after read a.txt 909783072