A copy of the generated code used in my blog post about Room database relationships.

UniversityDAO_Impl.java

package com.adammcneilly.androiduniversity.room;

import android.database.Cursor;
import androidx.collection.LongSparseArray;
import androidx.lifecycle.LiveData;
import androidx.room.RoomDatabase;
import androidx.room.RoomSQLiteQuery;
import androidx.room.util.CursorUtil;
import androidx.room.util.DBUtil;
import androidx.room.util.StringUtil;
import java.lang.Exception;
import java.lang.Override;
import java.lang.String;
import java.lang.StringBuilder;
import java.lang.SuppressWarnings;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;

@SuppressWarnings({"unchecked", "deprecation"})
public final class UniversityDAO_Impl implements UniversityDAO {
  private final RoomDatabase __db;

  public UniversityDAO_Impl(RoomDatabase __db) {
    this.__db = __db;
  }

  @Override
  public LiveData<List<StudentWithVehicles>> fetchStudentsWithVehicles() {
    final String _sql = "SELECT * FROM Student";
    final RoomSQLiteQuery _statement = RoomSQLiteQuery.acquire(_sql, 0);
    return __db.getInvalidationTracker().createLiveData(new String[]{"Vehicle","Student"}, true, new Callable<List<StudentWithVehicles>>() {
      @Override
      public List<StudentWithVehicles> call() throws Exception {
        __db.beginTransaction();
        try {
          final Cursor _cursor = DBUtil.query(__db, _statement, true, null);
          try {
            final int _cursorIndexOfStudentId = CursorUtil.getColumnIndexOrThrow(_cursor, "studentId");
            final int _cursorIndexOfFirstName = CursorUtil.getColumnIndexOrThrow(_cursor, "firstName");
            final int _cursorIndexOfLastName = CursorUtil.getColumnIndexOrThrow(_cursor, "lastName");
            final int _cursorIndexOfStreetName = CursorUtil.getColumnIndexOrThrow(_cursor, "address_streetName");
            final int _cursorIndexOfStreetNumber = CursorUtil.getColumnIndexOrThrow(_cursor, "address_streetNumber");
            final LongSparseArray<ArrayList<Vehicle>> _collectionVehicles = new LongSparseArray<ArrayList<Vehicle>>();
            while (_cursor.moveToNext()) {
              final long _tmpKey = _cursor.getLong(_cursorIndexOfStudentId);
              ArrayList<Vehicle> _tmpVehiclesCollection = _collectionVehicles.get(_tmpKey);
              if (_tmpVehiclesCollection == null) {
                _tmpVehiclesCollection = new ArrayList<Vehicle>();
                _collectionVehicles.put(_tmpKey, _tmpVehiclesCollection);
              }
            }
            _cursor.moveToPosition(-1);
            __fetchRelationshipVehicleAscomAdammcneillyAndroiduniversityRoomVehicle(_collectionVehicles);
            final List<StudentWithVehicles> _result = new ArrayList<StudentWithVehicles>(_cursor.getCount());
            while(_cursor.moveToNext()) {
              final StudentWithVehicles _item;
              final Student _tmpStudent;
              if (! (_cursor.isNull(_cursorIndexOfStudentId) && _cursor.isNull(_cursorIndexOfFirstName) && _cursor.isNull(_cursorIndexOfLastName) && _cursor.isNull(_cursorIndexOfStreetName) && _cursor.isNull(_cursorIndexOfStreetNumber))) {
                final long _tmpStudentId;
                _tmpStudentId = _cursor.getLong(_cursorIndexOfStudentId);
                final String _tmpFirstName;
                _tmpFirstName = _cursor.getString(_cursorIndexOfFirstName);
                final String _tmpLastName;
                _tmpLastName = _cursor.getString(_cursorIndexOfLastName);
                final Address _tmpAddress;
                if (! (_cursor.isNull(_cursorIndexOfStreetName) && _cursor.isNull(_cursorIndexOfStreetNumber))) {
                  final String _tmpStreetName;
                  _tmpStreetName = _cursor.getString(_cursorIndexOfStreetName);
                  final String _tmpStreetNumber;
                  _tmpStreetNumber = _cursor.getString(_cursorIndexOfStreetNumber);
                  _tmpAddress = new Address(_tmpStreetName,_tmpStreetNumber);
                }  else  {
                  _tmpAddress = null;
                }
                _tmpStudent = new Student(_tmpStudentId,_tmpFirstName,_tmpLastName,_tmpAddress);
              }  else  {
                _tmpStudent = null;
              }
              ArrayList<Vehicle> _tmpVehiclesCollection_1 = null;
              final long _tmpKey_1 = _cursor.getLong(_cursorIndexOfStudentId);
              _tmpVehiclesCollection_1 = _collectionVehicles.get(_tmpKey_1);
              if (_tmpVehiclesCollection_1 == null) {
                _tmpVehiclesCollection_1 = new ArrayList<Vehicle>();
              }
              _item = new StudentWithVehicles(_tmpStudent,_tmpVehiclesCollection_1);
              _result.add(_item);
            }
            __db.setTransactionSuccessful();
            return _result;
          } finally {
            _cursor.close();
          }
        } finally {
          __db.endTransaction();
        }
      }

      @Override
      protected void finalize() {
        _statement.release();
      }
    });
  }

  private void __fetchRelationshipVehicleAscomAdammcneillyAndroiduniversityRoomVehicle(final LongSparseArray<ArrayList<Vehicle>> _map) {
    if (_map.isEmpty()) {
      return;
    }
    // check if the size is too big, if so divide;
    if(_map.size() > RoomDatabase.MAX_BIND_PARAMETER_CNT) {
      LongSparseArray<ArrayList<Vehicle>> _tmpInnerMap = new LongSparseArray<ArrayList<Vehicle>>(androidx.room.RoomDatabase.MAX_BIND_PARAMETER_CNT);
      int _tmpIndex = 0;
      int _mapIndex = 0;
      final int _limit = _map.size();
      while(_mapIndex < _limit) {
        _tmpInnerMap.put(_map.keyAt(_mapIndex), _map.valueAt(_mapIndex));
        _mapIndex++;
        _tmpIndex++;
        if(_tmpIndex == RoomDatabase.MAX_BIND_PARAMETER_CNT) {
          __fetchRelationshipVehicleAscomAdammcneillyAndroiduniversityRoomVehicle(_tmpInnerMap);
          _tmpInnerMap = new LongSparseArray<ArrayList<Vehicle>>(RoomDatabase.MAX_BIND_PARAMETER_CNT);
          _tmpIndex = 0;
        }
      }
      if(_tmpIndex > 0) {
        __fetchRelationshipVehicleAscomAdammcneillyAndroiduniversityRoomVehicle(_tmpInnerMap);
      }
      return;
    }
    StringBuilder _stringBuilder = StringUtil.newStringBuilder();
    _stringBuilder.append("SELECT `vehicleId`,`ownerId`,`vehicleType` FROM `Vehicle` WHERE `ownerId` IN (");
    final int _inputSize = _map.size();
    StringUtil.appendPlaceholders(_stringBuilder, _inputSize);
    _stringBuilder.append(")");
    final String _sql = _stringBuilder.toString();
    final int _argCount = 0 + _inputSize;
    final RoomSQLiteQuery _stmt = RoomSQLiteQuery.acquire(_sql, _argCount);
    int _argIndex = 1;
    for (int i = 0; i < _map.size(); i++) {
      long _item = _map.keyAt(i);
      _stmt.bindLong(_argIndex, _item);
      _argIndex ++;
    }
    final Cursor _cursor = DBUtil.query(__db, _stmt, false, null);
    try {
      final int _itemKeyIndex = CursorUtil.getColumnIndex(_cursor, "ownerId");
      if (_itemKeyIndex == -1) {
        return;
      }
      final int _cursorIndexOfVehicleId = CursorUtil.getColumnIndex(_cursor, "vehicleId");
      final int _cursorIndexOfOwnerId = CursorUtil.getColumnIndex(_cursor, "ownerId");
      final int _cursorIndexOfVehicleType = CursorUtil.getColumnIndex(_cursor, "vehicleType");
      while(_cursor.moveToNext()) {
        final long _tmpKey = _cursor.getLong(_itemKeyIndex);
        ArrayList<Vehicle> _tmpRelation = _map.get(_tmpKey);
        if (_tmpRelation != null) {
          final Vehicle _item_1;
          final long _tmpVehicleId;
          if (_cursorIndexOfVehicleId == -1) {
            _tmpVehicleId = 0;
          } else {
            _tmpVehicleId = _cursor.getLong(_cursorIndexOfVehicleId);
          }
          final long _tmpOwnerId;
          if (_cursorIndexOfOwnerId == -1) {
            _tmpOwnerId = 0;
          } else {
            _tmpOwnerId = _cursor.getLong(_cursorIndexOfOwnerId);
          }
          final String _tmpVehicleType;
          if (_cursorIndexOfVehicleType == -1) {
            _tmpVehicleType = null;
          } else {
            _tmpVehicleType = _cursor.getString(_cursorIndexOfVehicleType);
          }
          _item_1 = new Vehicle(_tmpVehicleId,_tmpOwnerId,_tmpVehicleType);
          _tmpRelation.add(_item_1);
        }
      }
    } finally {
      _cursor.close();
    }
  }
}