CREATE TYPE TYPE_ENTRY_MAP AS OBJECT(
  key   VARCHAR2(80),
  value   VARCHAR2(80),
);

CREATE TYPE TYPE_MAP AS TABLE OF TYPE_ENTRY_MAP;

StructDescriptor entryType = StructDescriptor.createDescriptor("TYPE_ENTRY_MAP", _conn);
ArrayDescriptor mapType = ArrayDescriptor.createDescriptor("TYPE_MAP", _conn);
STRUCT[] entries = new STRUCT[...];
for (...) {
   Object[] objs = new Object[2];
   objs[0] = key;
   objs[1] = val;
   entries[i] = new STRUCT(entryType, _conn, objs);
}
ARRAY map = new ARRAY(mapType, _conn, entries);
stmt.setArray(..., map);