Disconnect a Ethernet Adapter always "Invalid configuration for device '0'."

I have a piece of code to disconnect the ethernet adapter from a virtual machine. But it always complains "Invalid configuration for device '0'." Anyone can help me figure out what can be wrong in my code?

VirtualEthernetCardNetworkBackingInfo backingInfo = new VirtualEthernetCardNetworkBackingInfo();        backingInfo.setDeviceName("Network adapter 1");        VirtualEthernetCard ethCard = new VirtualEthernetCard();        ethCard.setBacking(backingInfo);        VirtualDeviceConnectInfo connectInfo = new VirtualDeviceConnectInfo();        connectInfo.setConnected(false);        ethCard.setConnectable(connectInfo);        VirtualDeviceConfigSpec vdCfgSpec = new VirtualDeviceConfigSpec();        vdCfgSpec.setOperation(VirtualDeviceConfigSpecOperation.edit);        vdCfgSpec.setDevice(ethCard);        VirtualMachineConfigSpec vmConfigSpec = new VirtualMachineConfigSpec();        VirtualDeviceConfigSpec[] vdConfigSpecs = new VirtualDeviceConfigSpec[1];        vdConfigSpecs[0] = vdCfgSpec;        vmConfigSpec.setDeviceChange(vdConfigSpecs);        String status;        try {            Task task = virtualMachine.reconfigVM_Task(vmConfigSpec);            status = task.waitForTask();        } catch (Exception e) {
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