private static int DeleteWeakGlobalRef(VM_JNIEnvironment env) {
private static void DeleteWeakGlobalRef(VM_JNIEnvironment env, int refJREF) {
  private static int DeleteWeakGlobalRef(VM_JNIEnvironment env) {    if (traceJNI) VM.sysWrite("JNI called: DeleteWeakGlobalRef \n");       VM.sysWrite("JNI ERROR: DeleteWeakGlobalRef not implemented yet, exiting ...\n");    VM.sysExit(VM.exitStatusUnsupportedInternalOp);    return -1;   }