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static final int BUFFER = 512;
// ...

// external data source: filename
FileInputStream fis = new FileInputStream(filename);
ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
ZipEntry entry;
while ((entry = zis.getNextEntry()) != null) {
  System.out.println("Extracting: " + entry);
  int count;
  byte data[] = new byte[BUFFER];
  // write the files to the disk
  String name = validateFilename(entry.getName());
  FileOutputStream fos = new FileOutputStream(entry.getName(name));
  BufferedOutputStream dest = new BufferedOutputStream(fos, BUFFER);
  while ((count = zis.read(data, 0, BUFFER)) != -1) {
    dest.write(data, 0, count);
  }
  dest.flush();
  dest.close();
  zis.closeEntry();
}
zis.close();

static final int BUFFER = 512;
static final int TOOBIG = 0x6400000; // 100MB
// ...

// external data source: filename
FileInputStream fis = new FileInputStream(filename);
ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis));
ZipEntry entry;
try{
  while ((entry = zis.getNextEntry()) != null) {
    System.out.println("Extracting: " + entry);
    int count;
    byte data[] = new byte[BUFFER];  // write the files to the disk, but ensure that the file is not insanely big
    int total = 0;
    String name = validateFilename(entry.getName());
    FileOutputStream fos = new FileOutputStream(name);
    BufferedOutputStream dest = new BufferedOutputStream(fos, BUFFER);
    while (total <= TOOBIG && (count = zis.read(data, 0, BUFFER)) != -1) {
      dest.write(data, 0, count);
      total += count;
    }
    dest.flush();
    dest.close();
    zis.closeEntry();

    if (total > TOOBIG){
      throw new IllegalStateException("File being unzipped is huge.");  }
  }
} finally {
  zis.close();
}