code: package com.lody.virtual.server.device;
  
  import android.annotation.SuppressLint;
  import android.os.Build;
  import android.os.RemoteException;
  
  import com.lody.virtual.helper.collection.SparseArray;
  import com.lody.virtual.remote.VDeviceInfo;
  import com.lody.virtual.server.interfaces.IDeviceInfoManager;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Random;
  
  /**
   * @author Lody
   */
  
  public class VDeviceManagerService implements IDeviceInfoManager {
  
      private static VDeviceManagerService sInstance = new VDeviceManagerService();
      private final SparseArray<VDeviceInfo> mDeviceInfos = new SparseArray<>();
      private DeviceInfoPersistenceLayer mPersistenceLayer = new DeviceInfoPersistenceLayer(this);
      private UsedDeviceInfoPool mPool = new UsedDeviceInfoPool();
  
      public static VDeviceManagerService get() {
          return sInstance;
      }
  
      private final class UsedDeviceInfoPool {
          List<String> deviceIds = new ArrayList<>();
          List<String> androidIds = new ArrayList<>();
          List<String> wifiMacs = new ArrayList<>();
          List<String> bluetoothMacs = new ArrayList<>();
          List<String> iccIds = new ArrayList<>();
      }
  
      public VDeviceManagerService() {
          mPersistenceLayer.read();
          for (int i = 0; i < mDeviceInfos.size(); i++) {
              VDeviceInfo info = mDeviceInfos.valueAt(i);
              addDeviceInfoToPool(info);
          }
      }
  
      private void addDeviceInfoToPool(VDeviceInfo info) {
          mPool.deviceIds.add(info.deviceId);
          mPool.androidIds.add(info.androidId);
          mPool.wifiMacs.add(info.wifiMac);
          mPool.bluetoothMacs.add(info.bluetoothMac);
          mPool.iccIds.add(info.iccId);
      }
  
      @Override
      public VDeviceInfo getDeviceInfo(int userId) {
          VDeviceInfo info;
          synchronized (mDeviceInfos) {
              info = mDeviceInfos.get(userId);
              if (info == null) {
                  info = generateRandomDeviceInfo();
                  mDeviceInfos.put(userId, info);
                  mPersistenceLayer.save();
              }
          }
          return info;
      }
  
      @Override
      public void updateDeviceInfo(int userId, VDeviceInfo info) {
          synchronized (mDeviceInfos) {
              if (info != null) {
                  mDeviceInfos.put(userId, info);
                  mPersistenceLayer.save();
              }
          }
      }
  
      private VDeviceInfo generateRandomDeviceInfo() {
          VDeviceInfo info = new VDeviceInfo();
          String value;
          do {
              value = generate10(15);
              info.deviceId = value;
          } while (mPool.deviceIds.contains(value));
          do {
              value = generate16(16);
              info.androidId = value;
          } while (mPool.androidIds.contains(value));
          do {
              value = generateMac();
              info.wifiMac = value;
          } while (mPool.wifiMacs.contains(value));
          do {
              value = generateMac();
              info.bluetoothMac = value;
          } while (mPool.bluetoothMacs.contains(value));
  
          do {
              value = generate10(20);
              info.iccId = value;
          } while (mPool.iccIds.contains(value));
  
          info.serial = generateSerial();
  
          addDeviceInfoToPool(info);
          return info;
      }
  
  
      SparseArray<VDeviceInfo> getDeviceInfos() {
          return mDeviceInfos;
      }
  
      private static String generate10(int length) {
          Random random = new Random();
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i < length; i++) {
              sb.append(random.nextInt(10));
          }
          return sb.toString();
      }
  
      private static String generate16(int length) {
          Random random = new Random();
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i < length; i++) {
              int nextInt = random.nextInt(16);
              if (nextInt < 10) {
                  sb.append(nextInt);
              } else {
                  sb.append((char) (nextInt + 87));
              }
          }
          return sb.toString();
      }
  
      private static String generateMac() {
          Random random = new Random();
          StringBuilder sb = new StringBuilder();
          int next = 1;
          int cur = 0;
          while (cur < 12) {
              int val = random.nextInt(16);
              if (val < 10) {
                  sb.append(val);
              } else {
                  sb.append((char) (val + 87));
              }
              if (cur == next && cur != 11) {
                  sb.append(":");
                  next += 2;
              }
              cur++;
          }
          return sb.toString();
      }
  
      @SuppressLint("HardwareIds")
      private static String generateSerial() {
          String serial;
          if (Build.SERIAL == null || Build.SERIAL.length() <= 0) {
              serial = "0123456789ABCDEF";
          } else {
              serial = Build.SERIAL;
          }
          List<Character> list = new ArrayList<>();
          for (char c : serial.toCharArray()) {
              list.add(c);
          }
          Collections.shuffle(list);
          StringBuilder sb = new StringBuilder();
          for (Character c : list) {
              sb.append(c.charValue());
          }
          return sb.toString();
      }
  }
  