diff --git a/ompi/mpi/java/c/mpi_Comm.c b/ompi/mpi/java/c/mpi_Comm.c
index 68985fcefe..6b326eb625 100644
--- a/ompi/mpi/java/c/mpi_Comm.c
+++ b/ompi/mpi/java/c/mpi_Comm.c
@@ -1213,14 +1213,13 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iScatter(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_scatterv(
-        JNIEnv *env, jobject jthis,
+        JNIEnv *env, jobject jthis, jlong jComm,
         jobject sendBuf, jint sOffset, jintArray sCounts,
-        jintArray displs, jobject sJType,
-        jobject recvBuf, jint rOffset, jint rCount, jobject rJType,
-        jint root)
+        jintArray displs, jlong sjType, jint sBType,
+        jobject recvBuf, jint rOffset, jint rCount,
+        jlong rjType, jint rBType, jint root)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
+    MPI_Comm comm = (MPI_Comm)jComm;
     int id;
     int rc = MPI_Comm_rank(comm, &id);
     int rootOrInter = id == root || isInter(env, comm);
@@ -1230,40 +1229,31 @@ JNIEXPORT void JNICALL Java_mpi_Comm_scatterv(
 
     void *sPtr = NULL, *sBase, *rPtr, *rBase;
     MPI_Datatype rType;
-    int rBType;
 
-    if(rJType == NULL)
+    if(rjType == 0)
     {
         assert(recvBuf == NULL);
-        rType  = MPI_DATATYPE_NULL;
-        rBType = 0;
-        rPtr   = MPI_IN_PLACE;
-        rBase  = NULL;
+        rType = MPI_DATATYPE_NULL;
+        rPtr  = MPI_IN_PLACE;
+        rBase = NULL;
     }
     else
     {
-        rType = (MPI_Datatype)((*env)->GetLongField(
-                env, rJType, ompi_java.DatatypeHandle));
-
-        rBType = (*env)->GetIntField(env, rJType, ompi_java.DatatypeBaseType);
-        rPtr   = ompi_java_getBufPtr(&rBase, env, recvBuf, rBType, rOffset);
+        rType = (MPI_Datatype)rjType;
+        rPtr  = ompi_java_getBufPtr(&rBase, env, recvBuf, rBType, rOffset);
     }
 
     jint *jSCounts = NULL, *jDispls = NULL;
     int  *cSCounts = NULL, *cDispls = NULL;
     MPI_Datatype sType = rType;
-    int sBType;
 
     if(rootOrInter)
     {
         ompi_java_getIntArray(env, sCounts, &jSCounts, &cSCounts);
         ompi_java_getIntArray(env, displs, &jDispls, &cDispls);
 
-        sType = (MPI_Datatype)((*env)->GetLongField(
-                env, sJType, ompi_java.DatatypeHandle));
-
-        sBType = (*env)->GetIntField(env, sJType, ompi_java.DatatypeBaseType);
-        sPtr   = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
+        sType = (MPI_Datatype)sjType;
+        sPtr  = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
     }
 
     rc = MPI_Scatterv(sPtr, cSCounts, cDispls, sType,
@@ -1340,41 +1330,28 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iScatterv(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_allGather(
-        JNIEnv *env, jobject jthis,
-        jobject sendBuf, jint sOffset, jint sCount, jobject sendtype,
-        jobject recvBuf, jint rOffset, jint rCount, jobject recvtype)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jint sCount, jlong sjType, jint sBType,
+        jobject recvBuf, jint rOffset, jint rCount, jlong rjType, jint rBType)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-    int sBType;
+    MPI_Comm comm = (MPI_Comm)jComm;
     MPI_Datatype sType;
     void *sPtr, *sBase, *rPtr, *rBase;
 
-    if(sendtype == NULL)
+    if(sjType == 0)
     {
         assert(sendBuf == NULL);
-        sType  = MPI_DATATYPE_NULL;
-        sBType = 0;
-        sPtr   = MPI_IN_PLACE;
-        sBase  = NULL;
+        sType = MPI_DATATYPE_NULL;
+        sPtr  = MPI_IN_PLACE;
+        sBase = NULL;
     }
     else
     {
-        sType = (MPI_Datatype)((*env)->GetLongField(
-                env, sendtype, ompi_java.DatatypeHandle));
-
-        sBType = (*env)->GetIntField(env,
-                 sendtype, ompi_java.DatatypeBaseType);
-
-        sPtr = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
+        sType = (MPI_Datatype)sjType;
+        sPtr  = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
     }
 
-    MPI_Datatype rType = (MPI_Datatype)((*env)->GetLongField(
-                         env, recvtype, ompi_java.DatatypeHandle));
-
-    int rBType = (*env)->GetIntField(env,
-                 recvtype, ompi_java.DatatypeBaseType);
-
+    MPI_Datatype rType = (MPI_Datatype)rjType;
     rPtr = ompi_java_getBufPtr(&rBase, env, recvBuf, rBType, rOffset);
     int rc = MPI_Allgather(sPtr, sCount, sType, rPtr, rCount, rType, comm);
     ompi_java_exceptionCheck(env, rc);
@@ -1415,40 +1392,29 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iAllGather(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_allGatherv(
-        JNIEnv *env, jobject jthis,
-        jobject sendBuf, jint sOffset, jint sCount, jobject sJType,
-        jobject recvBuf, jint rOffset, jintArray rCounts,
-        jintArray displs, jobject rJType)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jint sCount, jlong sjType, jint sBType,
+        jobject recvBuf, jint rOffset, jintArray rCounts, jintArray displs,
+        jlong rjType, jint rBType)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
+    MPI_Comm comm = (MPI_Comm)jComm;
     void *sPtr, *sBase, *rPtr, *rBase;
     MPI_Datatype sType;
-    int sBType;
 
-    if(sJType == NULL)
+    if(sjType == 0)
     {
         assert(sendBuf == NULL);
-        sType  = MPI_DATATYPE_NULL;
-        sBType = 0;
-        sPtr   = MPI_IN_PLACE;
-        sBase  = NULL;
+        sType = MPI_DATATYPE_NULL;
+        sPtr  = MPI_IN_PLACE;
+        sBase = NULL;
     }
     else
     {
-        sType = (MPI_Datatype)((*env)->GetLongField(
-                env, sJType, ompi_java.DatatypeHandle));
-
-        sBType = (*env)->GetIntField(env, sJType, ompi_java.DatatypeBaseType);
-        sPtr   = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
+        sType = (MPI_Datatype)sjType;
+        sPtr  = ompi_java_getBufPtr(&sBase, env, sendBuf, sBType, sOffset);
     }
 
-    MPI_Datatype rType = (MPI_Datatype)((*env)->GetLongField(
-                         env, rJType, ompi_java.DatatypeHandle));
-
-    int rBType = (*env)->GetIntField(env, rJType, ompi_java.DatatypeBaseType);
-
+    MPI_Datatype rType = (MPI_Datatype)rjType;
     jint *jRCounts, *jDispls;
     int  *cRCounts, *cDispls;
     ompi_java_getIntArray(env, rCounts, &jRCounts, &cRCounts);
@@ -1506,20 +1472,13 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iAllGatherv(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_allToAll(
-        JNIEnv *env, jobject jthis,
-        jobject sendBuf, jint sOffset, jint sCount, jobject sJType,
-        jobject recvBuf, jint rOffset, jint rCount, jobject rJType)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jint sCount, jlong sjType, jint sBType,
+        jobject recvBuf, jint rOffset, jint rCount, jlong rjType, jint rBType)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
-    MPI_Datatype sType = (MPI_Datatype)((*env)->GetLongField(
-                         env, sJType, ompi_java.DatatypeHandle));
-    MPI_Datatype rType = (MPI_Datatype)((*env)->GetLongField(
-                         env, rJType, ompi_java.DatatypeHandle));
-
-    int sBType = (*env)->GetIntField(env, sJType, ompi_java.DatatypeBaseType);
-    int rBType = (*env)->GetIntField(env, rJType, ompi_java.DatatypeBaseType);
+    MPI_Comm     comm  = (MPI_Comm)jComm;
+    MPI_Datatype sType = (MPI_Datatype)sjType;
+    MPI_Datatype rType = (MPI_Datatype)rjType;
 
     void *sPtr, *sBase, *rPtr, *rBase;
     rPtr = ompi_java_getBufPtr(&rBase, env, recvBuf, rBType, rOffset);
@@ -1551,22 +1510,15 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iAllToAll(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_allToAllv(
-        JNIEnv *env, jobject jthis,
+        JNIEnv *env, jobject jthis, jlong jComm,
         jobject sendBuf, jint sOffset, jintArray sCount,
-        jintArray sDispls, jobject sJType,
+        jintArray sDispls, jlong sjType, jint sBType,
         jobject recvBuf, jint rOffset, jintArray rCount,
-        jintArray rDispls, jobject rJType)
+        jintArray rDispls, jlong rjType, jint rBType)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
-    MPI_Datatype sType = (MPI_Datatype)((*env)->GetLongField(
-                         env, sJType, ompi_java.DatatypeHandle));
-    MPI_Datatype rType = (MPI_Datatype)((*env)->GetLongField(
-                         env, rJType, ompi_java.DatatypeHandle));
-
-    int sBType = (*env)->GetIntField(env, sJType, ompi_java.DatatypeBaseType),
-        rBType = (*env)->GetIntField(env, rJType, ompi_java.DatatypeBaseType);
+    MPI_Comm     comm  = (MPI_Comm)jComm;
+    MPI_Datatype sType = (MPI_Datatype)sjType;
+    MPI_Datatype rType = (MPI_Datatype)rjType;
 
     jint *jSCount, *jRCount, *jSDispls, *jRDispls;
     int  *cSCount, *cRCount, *cSDispls, *cRDispls;
@@ -1622,12 +1574,11 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iAllToAllv(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_reduce(
-        JNIEnv *env, jobject jthis, jobject sendBuf, jint sOffset,
-        jobject recvBuf, jint rOffset, jint count, jobject type,
-        jobject op, jint root)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jobject recvBuf, jint rOffset,
+        jint count, jlong jType, jint baseType, jobject op, jint root)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
+    MPI_Comm comm = (MPI_Comm)jComm;
     int id;
     int rc = MPI_Comm_rank(comm, &id);
     int rootOrInter = id == root || isInter(env, comm);
@@ -1635,10 +1586,7 @@ JNIEXPORT void JNICALL Java_mpi_Comm_reduce(
     if(ompi_java_exceptionCheck(env, rc))
         return;
 
-    MPI_Datatype mpiType = (MPI_Datatype)((*env)->GetLongField(
-                           env, type, ompi_java.DatatypeHandle));
-
-    int baseType = (*env)->GetIntField(env, type, ompi_java.DatatypeBaseType);
+    MPI_Datatype type = (MPI_Datatype)jType;
     void *sPtr, *sBase, *rPtr = NULL, *rBase;
 
     if(sendBuf == NULL)
@@ -1662,7 +1610,7 @@ JNIEXPORT void JNICALL Java_mpi_Comm_reduce(
     }
 
     MPI_Op mpiOp = ompi_java_op_getHandle(env, op, baseType);
-    rc = MPI_Reduce(sPtr, rPtr, count, mpiType, mpiOp, root, comm);
+    rc = MPI_Reduce(sPtr, rPtr, count, type, mpiOp, root, comm);
     ompi_java_exceptionCheck(env, rc);
 
     if(sendBuf != NULL)
@@ -1717,18 +1665,12 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iReduce(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_allReduce(
-                       JNIEnv *env, jobject jthis,
-                       jobject sendBuf, jint sendOffset,
-                       jobject recvBuf, jint recvOffset,
-                       jint count, jobject type, jobject op)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sendOffset, jobject recvBuf, jint recvOffset,
+        jint count, jlong jType, jint baseType, jobject op)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
-    MPI_Datatype mpiType = (MPI_Datatype)((*env)->GetLongField(
-                           env, type, ompi_java.DatatypeHandle));
-
-    int baseType = (*env)->GetIntField(env, type, ompi_java.DatatypeBaseType);
+    MPI_Comm     comm = (MPI_Comm)jComm;
+    MPI_Datatype type = (MPI_Datatype)jType;
     void *sPtr, *sBase, *rPtr, *rBase;
 
     if(sendBuf == NULL)
@@ -1738,7 +1680,7 @@ JNIEXPORT void JNICALL Java_mpi_Comm_allReduce(
 
     rPtr = ompi_java_getBufPtr(&rBase, env, recvBuf, baseType, recvOffset);
     MPI_Op mpiOp = ompi_java_op_getHandle(env, op, baseType);
-    int rc = MPI_Allreduce(sPtr, rPtr, count, mpiType, mpiOp, comm);
+    int rc = MPI_Allreduce(sPtr, rPtr, count, type, mpiOp, comm);
     ompi_java_exceptionCheck(env, rc);
 
     ompi_java_releaseBufPtr(env, recvBuf, rBase, baseType);
@@ -1771,17 +1713,12 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iAllReduce(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_reduceScatter(
-        JNIEnv *env, jobject jthis, jobject sendBuf, jint sOffset,
-        jobject recvBuf, jint rOffset, jintArray rCounts,
-        jobject jType, jobject op)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jobject recvBuf, jint rOffset,
+        jintArray rCounts, jlong jType, jint bType, jobject op)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
-    MPI_Datatype type = (MPI_Datatype)((*env)->GetLongField(
-                        env, jType, ompi_java.DatatypeHandle));
-
-    int bType = (*env)->GetIntField(env, jType, ompi_java.DatatypeBaseType);
+    MPI_Comm     comm = (MPI_Comm)jComm;
+    MPI_Datatype type = (MPI_Datatype)jType;
     void *sPtr, *sBase, *rPtr, *rBase;
 
     if(sendBuf == NULL)
@@ -1835,16 +1772,12 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iReduceScatter(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_reduceScatterBlock(
-        JNIEnv *env, jobject jthis, jobject sendBuf, jint sOffset,
-        jobject recvBuf, jint rOffset, jint count, jobject jType, jobject op)
+        JNIEnv *env, jobject jthis, jlong jComm,
+        jobject sendBuf, jint sOffset, jobject recvBuf, jint rOffset,
+        jint count, jlong jType, jint bType, jobject op)
 {
-    MPI_Comm comm = (MPI_Comm)((*env)->GetLongField(
-                    env, jthis, ompi_java.CommHandle));
-
-    MPI_Datatype type = (MPI_Datatype)((*env)->GetLongField(
-                        env, jType, ompi_java.DatatypeHandle));
-
-    int bType = (*env)->GetIntField(env, jType, ompi_java.DatatypeBaseType);
+    MPI_Comm     comm = (MPI_Comm)jComm;
+    MPI_Datatype type = (MPI_Datatype)jType;
     void *sPtr, *sBase, *rPtr, *rBase;
 
     if(sendBuf == NULL)
@@ -1887,23 +1820,21 @@ JNIEXPORT jlong JNICALL Java_mpi_Comm_iReduceScatterBlock(
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_reduceLocal(
-        JNIEnv *env, jobject jthis, jobject inbuf, jint inoff,
-        jobject inoutbuf, jint inoutoff, jint count, jobject type, jobject op)
+        JNIEnv *env, jclass clazz, jobject inBuf, jint inOff,
+        jobject inOutBuf, jint inOutOff, jint count,
+        jlong jType, jint bType, jobject op)
 {
-    MPI_Datatype mpi_type =
-        (MPI_Datatype)((*env)->GetLongField(env,type,ompi_java.DatatypeHandle));
+    MPI_Datatype type = (MPI_Datatype)jType;
+    void *inPtr, *inBase, *inOutPtr, *inOutBase;
+    inPtr = getBufCritical(&inBase, env, inBuf, bType, inOff);
+    inOutPtr = getBufCritical(&inOutBase, env, inOutBuf, bType, inOutOff);
 
-    int baseType = (*env)->GetIntField(env, type, ompi_java.DatatypeBaseType);
-    void *inptr, *inbase, *inoutptr, *inoutbase;
-    inptr = ompi_java_getBufPtr(&inbase, env, inbuf, baseType, inoff);
-    inoutptr = ompi_java_getBufPtr(&inoutbase, env, inoutbuf, baseType, inoutoff);
-
-    int rc = MPI_Reduce_local(inptr, inoutptr, count, mpi_type,
-                              ompi_java_op_getHandle(env, op, baseType));
+    int rc = MPI_Reduce_local(inPtr, inOutPtr, count, type,
+                              ompi_java_op_getHandle(env, op, bType));
 
     ompi_java_exceptionCheck(env, rc);
-    ompi_java_releaseReadBufPtr(env, inbuf, inbase, baseType);
-    ompi_java_releaseBufPtr(env, inoutbuf, inoutbase, baseType);
+    releaseBufCritical(env, inBuf, inBase);
+    releaseBufCritical(env, inOutBuf, inOutBase);
 }
 
 JNIEXPORT void JNICALL Java_mpi_Comm_setName(
diff --git a/ompi/mpi/java/java/Comm.java b/ompi/mpi/java/java/Comm.java
index 7dca99eef3..039de68913 100644
--- a/ompi/mpi/java/java/Comm.java
+++ b/ompi/mpi/java/java/Comm.java
@@ -1613,8 +1613,10 @@ public final void scatterv(
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    scatterv(sendbuf, sendoff, sendcount, displs, sendtype,
-             recvbuf, recvoff, recvcount, recvtype, root);
+    scatterv(handle, sendbuf, sendoff, sendcount, displs,
+             sendtype.handle, sendtype.baseType,
+             recvbuf, recvoff, recvcount,
+             recvtype.handle, recvtype.baseType, root);
 }
 
 /**
@@ -1642,8 +1644,9 @@ public final void scatterv(Object sendbuf, int[] sendcount, int[] displs,
         sendbuf = ((Buffer)sendbuf).array();
     }
 
-    scatterv(sendbuf, sendoff, sendcount, displs, sendtype,
-             null, 0, 0, null, root);
+    scatterv(handle, sendbuf, sendoff, sendcount, displs,
+             sendtype.handle, sendtype.baseType,
+             null, 0, 0, 0, 0, root);
 }
 
 /**
@@ -1670,15 +1673,16 @@ public final void scatterv(Object recvbuf, int recvcount,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    scatterv(null, 0, null, null, null,
-             recvbuf, recvoff, recvcount, recvtype, root);
+    scatterv(handle, null, 0, null, null, 0, 0,
+             recvbuf, recvoff, recvcount,
+             recvtype.handle, recvtype.baseType, root);
 }
 
 private native void scatterv(
-        Object sendbuf, int sendoffset,
-        int[] sendcount, int[] displs, Datatype sendtype,
-        Object recvbuf, int recvoffset, int recvcount,
-        Datatype recvtype, int root)
+        long comm, Object sendBuf, int sendOffset,
+        int[] sendCount, int[] displs, long sendType, int sendBaseType,
+        Object recvBuf, int recvOffset, int recvCount,
+        long recvType, int recvBaseType, int root)
         throws MPIException;
 
 /**
@@ -1792,8 +1796,10 @@ public final void allGather(Object sendbuf, int sendcount, Datatype sendtype,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allGather(sendbuf, sendoff, sendcount, sendtype,
-              recvbuf, recvoff, recvcount, recvtype);
+    allGather(handle, sendbuf, sendoff, sendcount,
+              sendtype.handle, sendtype.baseType,
+              recvbuf, recvoff, recvcount,
+              recvtype.handle, recvtype.baseType);
 }
 
 /**
@@ -1817,13 +1823,15 @@ public final void allGather(Object buf, int count, Datatype type)
         buf = ((Buffer)buf).array();
     }
 
-    allGather(null, 0, 0, null, buf, off, count, type);
+    allGather(handle, null, 0, 0, 0, 0,
+              buf, off, count, type.handle, type.baseType);
 }
 
 private native void allGather(
-        Object sendbuf, int sendoffset, int sendcount, Datatype sendtype,
-        Object recvbuf, int recvoffset, int recvcount, Datatype recvtype)
-        throws MPIException;
+        long comm, Object sendBuf, int sendOffset, int sendCount,
+        long sendType, int sendBaseType,
+        Object recvBuf, int recvOffset, int recvCount,
+        long recvType, int recvBaseType) throws MPIException;
 
 /**
  * Similar to {@code gather}, but all processes receive the result.
@@ -1905,8 +1913,10 @@ public final void allGatherv(
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allGatherv(sendbuf, sendoff, sendcount, sendtype,
-               recvbuf, recvoff, recvcount, displs, recvtype);
+    allGatherv(handle, sendbuf, sendoff, sendcount,
+               sendtype.handle, sendtype.baseType,
+               recvbuf, recvoff, recvcount, displs,
+               recvtype.handle, recvtype.baseType);
 }
 
 /**
@@ -1932,13 +1942,15 @@ public final void allGatherv(Object recvbuf, int[] recvcount,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allGatherv(null, 0, 0, null, recvbuf, recvoff, recvcount, displs, recvtype);
+    allGatherv(handle, null, 0, 0, 0, 0, recvbuf, recvoff, recvcount,
+               displs, recvtype.handle, recvtype.baseType);
 }
 
 private native void allGatherv(
-        Object sendbuf, int sendoffset, int sendcount, Datatype sendtype,
-        Object recvbuf, int recvoffset, int[] recvcount, int[] displs,
-        Datatype recvtype) throws MPIException;
+        long comm, Object sendBuf, int sendOffset, int sendCount,
+        long sendType, int sendBaseType,
+        Object recvBuf, int recvOffset, int[] recvCount, int[] displs,
+        long recvType, int recvBasetype) throws MPIException;
 
 /**
  * Similar to {@code gatherv}, but all processes receive the result.
@@ -2026,14 +2038,17 @@ public final void allToAll(Object sendbuf, int sendcount, Datatype sendtype,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allToAll(sendbuf, sendoff, sendcount, sendtype,
-             recvbuf, recvoff, recvcount, recvtype);
+    allToAll(handle, sendbuf, sendoff, sendcount,
+             sendtype.handle, sendtype.baseType,
+             recvbuf, recvoff, recvcount,
+             recvtype.handle, recvtype.baseType);
 }
 
 private native void allToAll(
-        Object sendbuf, int sendoffset, int sendcount, Datatype sendtype,
-        Object recvbuf, int recvoffset, int recvcount, Datatype recvtype)
-        throws MPIException;
+        long comm, Object sendBuf, int sendOffset, int sendCount,
+        long sendType, int sendBaseType,
+        Object recvBuf, int recvOffset, int recvCount,
+        long recvType, int recvBaseType) throws MPIException;
 
 /**
  * Extension of {@code allGather} to the case where each process sends
@@ -2100,15 +2115,17 @@ public final void allToAllv(
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allToAllv(sendbuf, sendoff, sendcount, sdispls, sendtype,
-              recvbuf, recvoff, recvcount, rdispls, recvtype);
+    allToAllv(handle, sendbuf, sendoff, sendcount, sdispls,
+              sendtype.handle, sendtype.baseType,
+              recvbuf, recvoff, recvcount, rdispls,
+              recvtype.handle, recvtype.baseType);
 }
 
 private native void allToAllv(
-        Object sendbuf, int sendoffset,
-        int[] sendcount, int[] sdispls, Datatype sendtype,
-        Object recvbuf, int recvoffset,
-        int[] recvcount, int[] rdispls, Datatype recvtype)
+        long comm, Object sendBuf, int sendOffset,
+        int[] sendCount, int[] sdispls, long sendType, int sendBaseType,
+        Object recvBuf, int recvOffset,
+        int[] recvCount, int[] rdispls, long recvType, int recvBaseType)
         throws MPIException;
 
 /**
@@ -2186,7 +2203,8 @@ public final void reduce(Object sendbuf, Object recvbuf, int count,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    reduce(sendbuf, sendoff, recvbuf, recvoff, count, type, op, root);
+    reduce(handle, sendbuf, sendoff, recvbuf, recvoff, count,
+           type.handle, type.baseType, op, root);
 }
 
 /**
@@ -2215,12 +2233,14 @@ public final void reduce(Object buf, int count, Datatype type, Op op, int root)
         buf = ((Buffer)buf).array();
     }
 
-    reduce(null, 0, buf, off, count, type, op, root);
+    reduce(handle, null, 0, buf, off, count,
+           type.handle, type.baseType, op, root);
 }
 
 private native void reduce(
-        Object sendbuf, int sendoff, Object recvbuf, int recvoff,
-        int count, Datatype type, Op op, int root) throws MPIException;
+        long comm, Object sendbuf, int sendoff, Object recvbuf, int recvoff,
+        int count, long type, int baseType, Op op, int root)
+        throws MPIException;
 
 /**
  * Combine elements in input buffer of each process using the reduce
@@ -2311,7 +2331,8 @@ public final void allReduce(Object sendbuf, Object recvbuf,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    allReduce(sendbuf, sendoff, recvbuf, recvoff, count, type, op);
+    allReduce(handle, sendbuf, sendoff, recvbuf, recvoff, count,
+              type.handle, type.baseType, op);
 }
 
 /**
@@ -2338,12 +2359,12 @@ public final void allReduce(Object buf, int count, Datatype type, Op op)
         buf = ((Buffer)buf).array();
     }
 
-    allReduce(null, 0, buf, off, count, type, op);
+    allReduce(handle, null, 0, buf, off, count, type.handle, type.baseType, op);
 }
 
 private native void allReduce(
-        Object sendbuf, int sendoff, Object recvbuf, int recvoff,
-        int count, Datatype type, Op op) throws MPIException;
+        long comm, Object sendbuf, int sendoff, Object recvbuf, int recvoff,
+        int count, long type, int baseType, Op op) throws MPIException;
 
 /**
  * Same as {@code reduce} except that the result appears in receive
@@ -2430,7 +2451,8 @@ public final void reduceScatter(Object sendbuf, Object recvbuf,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    reduceScatter(sendbuf, sendoff, recvbuf, recvoff, recvcounts, type, op);
+    reduceScatter(handle, sendbuf, sendoff, recvbuf, recvoff, recvcounts,
+                  type.handle, type.baseType, op);
 }
 
 /**
@@ -2458,12 +2480,13 @@ public final void reduceScatter(Object buf, int[] counts, Datatype type, Op op)
         buf = ((Buffer)buf).array();
     }
 
-    reduceScatter(null, 0, buf, off, counts, type, op);
+    reduceScatter(handle, null, 0, buf, off, counts,
+                  type.handle, type.baseType, op);
 }
 
 private native void reduceScatter(
-        Object sendbuf, int sendoff, Object recvbuf, int recvoff,
-        int[] recvcounts, Datatype type, Op op) throws MPIException;
+        long comm, Object sendbuf, int sendoff, Object recvbuf, int recvoff,
+        int[] recvcounts, long type, int baseType, Op op) throws MPIException;
 
 /**
  * Combine elements in input buffer of each process using the reduce
@@ -2551,7 +2574,8 @@ public final void reduceScatterBlock(Object sendbuf, Object recvbuf,
         recvbuf = ((Buffer)recvbuf).array();
     }
 
-    reduceScatterBlock(sendbuf, sendoff, recvbuf, recvoff, recvcount, type, op);
+    reduceScatterBlock(handle, sendbuf, sendoff, recvbuf, recvoff, recvcount,
+                       type.handle, type.baseType, op);
 }
 
 /**
@@ -2578,12 +2602,13 @@ public final void reduceScatterBlock(
         buf = ((Buffer)buf).array();
     }
 
-    reduceScatterBlock(null, 0, buf, off, count, type, op);
+    reduceScatterBlock(handle, null, 0, buf, off, count,
+                       type.handle, type.baseType, op);
 }
 
 private native void reduceScatterBlock(
-        Object sendbuf, int sendoffset, Object recvbuf, int recvoffset,
-        int recvcount, Datatype type, Op op) throws MPIException;
+        long comm, Object sendBuf, int sOffset, Object recvBuf, int rOffset,
+        int rCount, long type, int baseType, Op op) throws MPIException;
 
 /**
  * Combine values and scatter the results.
@@ -2637,44 +2662,45 @@ private native long iReduceScatterBlock(
 
 /**
  * Apply the operation given by {@code op} element-wise to the
- * elements of {@code inbuf} and {@code inoutbuf} with the result
- * stored element-wise in {@code inoutbuf}.
+ * elements of {@code inBuf} and {@code inOutBuf} with the result
+ * stored element-wise in {@code inOutBuf}.
  * <p>Java binding of the MPI operation {@code MPI_REDUCE_LOCAL}.
- * @param inbuf    input buffer array
- * @param inoutbuf input buffer array, will contain combined output
+ * @param inBuf    input buffer array
+ * @param inOutBuf input buffer array, will contain combined output
  * @param count    number of elements
  * @param type     data type of each item
  * @param op       reduce operation
  * @throws MPIException
  */
-public final void reduceLocal(Object inbuf, Object inoutbuf, int count,
-                              Datatype type, Op op)
+public static void reduceLocal(
+        Object inBuf, Object inOutBuf, int count, Datatype type, Op op)
     throws MPIException
 {
     MPI.check();
     op.setDatatype(type);
 
-    int inoff    = 0,
-        inoutoff = 0;
+    int inOff    = 0,
+        inOutOff = 0;
 
-    if(isHeapBuffer(inbuf))
+    if(isHeapBuffer(inBuf))
     {
-        inoff = ((Buffer)inbuf).arrayOffset();
-        inbuf = ((Buffer)inbuf).array();
+        inOff = ((Buffer)inBuf).arrayOffset();
+        inBuf = ((Buffer)inBuf).array();
     }
 
-    if(isHeapBuffer(inoutbuf))
+    if(isHeapBuffer(inOutBuf))
     {
-        inoutoff = ((Buffer)inoutbuf).arrayOffset();
-        inoutbuf = ((Buffer)inoutbuf).array();
+        inOutOff = ((Buffer)inOutBuf).arrayOffset();
+        inOutBuf = ((Buffer)inOutBuf).array();
     }
 
-    reduceLocal(inbuf, inoff, inoutbuf, inoutoff, count, type, op);
+    reduceLocal(inBuf, inOff, inOutBuf, inOutOff, count,
+                type.handle, type.baseType, op);
 }
 
-private native void reduceLocal(
-        Object inbuf, int inoff, Object inoutbuf, int inoutoff,
-        int count, Datatype datatype, Op op) throws MPIException;
+private static native void reduceLocal(
+        Object inBuf, int inOff, Object inOutBuf, int inOutOff,
+        int count, long type, int baseType, Op op) throws MPIException;
 
 /**
  * Sets the print name for the communicator.