How to check whether a particular device supports 4G networks in Android?

This might work. It should check for WiMax 4g:

    private boolean is4gavailable() {
    ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo mobileInfo = connec.getNetworkInfo(0);
    NetworkInfo wifiInfo = connec.getNetworkInfo(1);
    NetworkInfo wimaxInfo = connec.getNetworkInfo(6);


    if (wimaxInfo!=null) {
    return mobileInfo.isConnectedOrConnecting() || wifiInfo.isConnectedOrConnecting() || wimaxInfo.isConnectedOrConnecting();
    }
    else {
    return mobileInfo.isConnectedOrConnecting() || wifiInfo.isConnectedOrConnecting();
    }
}

Try looking at this for a little more clarification.

ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
   NetworkInfo[] info = cm.getAllNetworkInfo();
   for(int i=0; i <info.length; i++){
       Log.i("netinfo"+i, info[i].getType()+"");
       Log.i("netinfo"+i, info[i].getTypeName());
       Log.i("netinfo"+i, info[i].getSubtype()+"");
       Log.i("netinfo"+i, info[i].getSubtypeName());
   }

Use this piece of code and get all available options on the device. I think you should be able to get all capabilities of the device.

and network type info is present in http://developer.android.com/reference/android/telephony/TelephonyManager.html.

I think network types added from API level 11 are for 4g. Check it yourself.