static void setDefaultVMArgs(S args) {
  S oldArgs = javaxDefaultVMArgs();
  args = trim(args);
  if (neq(unnull(oldArgs), unnull(args))) {
    print();
    print("Changing default VM arguments from");
    print("  " + oldArgs);
    print("to");
    print("  " + args);
    print();
    saveTextFile(javaxDataDir("default-vm-args"), nullIfEmpty(args));
  }
}

Began life as a copy of #1005864