cdm/src/main/java/ucar/nc2/iosp/misc/Nldn.java
public boolean isValidFile(RandomAccessFile raf) throws IOException {
    raf.seek(0);
    String test = raf.readString(MAGIC.length());
    return test.equals(MAGIC);
  }
public boolean isValidFile(RandomAccessFile raf) throws IOException {
    raf.seek(0);
    String test = raf.readString(MAGIC.length());
    return test.equals(MAGIC);
  }
Check if this is a valid file for this IOServiceProvider.
You must make this method thread safe, ie dont keep any state.

@param raf RandomAccessFile
@return true if valid.
@throws IOException if read error