Re: [netcdf-java] NoSuchMethodError

Hello Bob

I have already meet the exact same error with other software. It seems to be caused by a hole in a compatibility later of Java compiler. More specifically, it is possible to compile a library for Java 8 using a more recent Java version, for example 17, by specifying the following option to the Java compiler:

   --release 8

Maybe this is what the netCDF project does. When this option is given to javac, the compiler uses some list of what methods were available in Java 8, and generate a compiler error if we try to use a Java 17 method which was not available in Java 8.

Unfortunately there is apparently a grey area not well covered by above mechanism: covariant return type. The following method existed (indirectly) in Java 8. I said "indirectly" because it was actually inherited from the Buffer parent class:

   public class ByteBuffer extends Buffer {
        public*Buffer*  flip();

However in Java 9, above method has been overridden has below: the return type has been specialized from Buffer to ByteBuffer (this is "return type covariance").

   public class ByteBuffer extends Buffer {
        public*ByteBuffer*  flip();

From Java language point of view, methods with the same signature but covariant return type are the same method. But from the JVM point of view, if the return type is not exactly the same, this is considered as two completely different methods. Normally the Java compiler handles those difference by generating synthetic methods (invisible to Java developers, except in stack trace when an exception is thrown).

So I believe that this is a hole in the compatibility later of javac, where it did not recognize that the call to "ByteBuffer flip()" needs to be replaced by "Buffer flip()". There is two ways to fix this problem:

 * Compile with Java 8.
 * Or modify the source code with the following change in every place
   where a flip() or similar method is invoked on a Buffer subclass:




   ((Buffer) buffer).flip();

  • 2021 messages navigation, sorted by:
    1. Thread
    2. Subject
    3. Author
    4. Date
    5. ↑ Table Of Contents
  • Search the netcdf-java archives: