Note that the HDF5 Java library contains native methods. Hence, you need to download the appropriate native library for hdf-java (usually a .dll or .so file). The location path of the native library must be specified by setting the java.library.path system property:
java -Djava.library.path=PATH_TO_HDF_LIB ...
For details about the HDF5 format, see http://www.hdfgroup.org.