running blcokStats() with Java binding (libvirt-java-0.2.1 ) I get an exception Inspecting the src/jni/org_libvirt_Domain.c is see the following lines of code : JNIEXPORT jobject JNICALL Java_org_libvirt_Domain__1blockStats (JNIEnv *env, jobject obj, jlong VDP, jstring j_path){ struct _virDomainBlockStats stats; jobject j_stats; jclass stats_cls=(*env)->FindClass(env, "org/libvirt/DomainInterfaceStats"); const char *path = (*env)->GetStringUTFChars(env, j_path, NULL); if(virDomainBlockStats((virDomainPtr)VDP, path, &stats, sizeof(struct _virDomainBlockStats))<0){ (*env)->ReleaseStringUTFChars(env, j_path, path); return NULL; } . . . The bold line should be replaced by : jclass stats_cls=(*env)->FindClass(env, "org/libvirt/DomainBlockStats") as we deal here with blockStats and not network interface Stats ! thanks Zvi Dubitzky Virtualization and System Architecture Email:dubi@il.ibm.com IBM Haifa Research Laboratory Phone: +972-4-8296182 Haifa, 31905, ISRAEL