The following table lists all of the Java basic simple type and their corresponding C/C++ and MPI datatype.
Java datatype C/C++ datatype MPI datatype byte signed char MPI_CHAR char signed short int MPI_SHORT short signed short int MPI_SHORT boolean signed long int MPI_LONG int signed long int MPI_LONG long signed long long int MPI_LONG_LONG_INT float float MPI_FLOAT double double MPI_DOUBLEBecause Java is platform independent, the size of simple type will be the same in all platforms. So in order to fit into some system that has 64bits pointer, we use the long in Java to store the MPI object handle or pointer reference.