code: package com.lody.virtual.server.am;
  
  import com.lody.virtual.helper.utils.FileUtils;
  import com.lody.virtual.helper.utils.VLog;
  import com.lody.virtual.os.VEnvironment;
  import com.lody.virtual.server.pm.parser.VPackage;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.util.HashMap;
  import java.util.Map;
  
  import static android.os.Process.FIRST_APPLICATION_UID;
  
  /**
   * @author Lody
   */
  
  public class UidSystem {
  
      private static final String TAG = UidSystem.class.getSimpleName();
  
      private final HashMap<String, Integer> mSharedUserIdMap = new HashMap<>();
      private int mFreeUid = FIRST_APPLICATION_UID;
  
  
      public void initUidList() {
          mSharedUserIdMap.clear();
          File uidFile = VEnvironment.getUidListFile();
          if (!loadUidList(uidFile)) {
              File bakUidFile = VEnvironment.getBakUidListFile();
              loadUidList(bakUidFile);
          }
      }
  
      private boolean loadUidList(File uidFile) {
          if (!uidFile.exists()) {
              return false;
          }
          try {
              ObjectInputStream is = new ObjectInputStream(new FileInputStream(uidFile));
              mFreeUid = is.readInt();
              //noinspection unchecked
              Map<String, Integer> map = (HashMap<String, Integer>) is.readObject();
              mSharedUserIdMap.putAll(map);
              is.close();
          } catch (Throwable e) {
              return false;
          }
          return true;
      }
  
      private void save() {
          File uidFile = VEnvironment.getUidListFile();
          File bakUidFile = VEnvironment.getBakUidListFile();
          if (uidFile.exists()) {
              if (bakUidFile.exists() && !bakUidFile.delete()) {
                  VLog.w(TAG, "Warning: Unable to delete the expired file --\n " + bakUidFile.getPath());
              }
              try {
                  FileUtils.copyFile(uidFile, bakUidFile);
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          try {
              ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(uidFile));
              os.writeInt(mFreeUid);
              os.writeObject(mSharedUserIdMap);
              os.close();
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      public int getOrCreateUid(VPackage pkg) {
          String sharedUserId = pkg.mSharedUserId;
          if (sharedUserId == null) {
              sharedUserId = pkg.packageName;
          }
          Integer uid = mSharedUserIdMap.get(sharedUserId);
          if (uid != null) {
              return uid;
          }
          int newUid = ++mFreeUid;
          mSharedUserIdMap.put(sharedUserId, newUid);
          save();
          return newUid;
      }
  }
  