room/runtime/src/main/java/androidx/room/RoomDatabase.java
@NonNull
        public Builder<T> fallbackToDestructiveMigrationFrom(int... startVersions) {
            if (mMigrationsNotRequiredFrom == null) {
                mMigrationsNotRequiredFrom = new HashSet<>(startVersions.length);
            }
            for (int startVersion : startVersions) {
                mMigrationsNotRequiredFrom.add(startVersion);
            }
            return this;
        }
/**
         * Informs Room that it is allowed to destructively recreate database tables from specific
         * starting schema versions.
         * <p>
         * This functionality is the same as that provided by
         * {@link #fallbackToDestructiveMigration()}, except that this method allows the
         * specification of a set of schema versions for which destructive recreation is allowed.
         * <p>
         * Using this method is preferable to {@link #fallbackToDestructiveMigration()} if you want
         * to allow destructive migrations from some schema versions while still taking advantage
         * of exceptions being thrown due to unintentionally missing migrations.
         * <p>
         * Note: No versions passed to this method may also exist as either starting or ending
         * versions in the {@link Migration}s provided to {@link #addMigrations(Migration...)}. If a
         * version passed to this method is found as a starting or ending version in a Migration, an
         * exception will be thrown.
         *
         * @param startVersions The set of schema versions from which Room should use a destructive
         *                      migration.
         * @return this
         */
Informs Room that it is allowed to destructively recreate database tables from specific
starting schema versions.

This functionality is the same as that provided by
#fallbackToDestructiveMigration(), except that this method allows the
specification of a set of schema versions for which destructive recreation is allowed.

Using this method is preferable to  #fallbackToDestructiveMigration() if you want
to allow destructive migrations from some schema versions while still taking advantage
of exceptions being thrown due to unintentionally missing migrations.

Note: No versions passed to this method may also exist as either starting or ending
versions in the  Migrations provided to  #addMigrations(Migration...). If a
version passed to this method is found as a starting or ending version in a Migration, an
exception will be thrown.

@param startVersions The set of schema versions from which Room should use a destructive
migration.
@return this
Informs Room that it is allowed to destructively recreate database tables from specific starting schema versions . This functionality is the same as that provided by #fallbackToDestructiveMigration () except that this method allows the specification of a set of schema versions for which destructive recreation is allowed . Using this method is preferable to #fallbackToDestructiveMigration () if you want to allow destructive migrations from some schema versions while still taking advantage of exceptions being thrown due to unintentionally missing migrations . Note : No versions passed to this method may also exist as either starting or ending versions in the Migrations provided to #addMigrations ( Migration ... ) . If a version passed to this method is found as a starting or ending version in a Migration an exception will be thrown . @param startVersions The set of schema versions from which Room should use a destructive migration . @return this
@NonNull
        public Builder<T> fallbackToDestructiveMigrationFrom(int... startVersions) {
            if (mMigrationsNotRequiredFrom == null) {
                mMigrationsNotRequiredFrom = new HashSet<>(startVersions.length);
            }
            for (int startVersion : startVersions) {
                mMigrationsNotRequiredFrom.add(startVersion);
            }
            return this;
        }
@ NonNull public Builder < T > fallbackToDestructiveMigrationFrom ( int ... startVersions ) { if ( mMigrationsNotRequiredFrom == null ) { mMigrationsNotRequiredFrom = new HashSet < > ( startVersions . length ) ; } for ( int startVersion : startVersions ) { mMigrationsNotRequiredFrom . add ( startVersion ) ; } return this ; }
Informs Room that it is allowed to destructively recreate database tables from specific
 starting schema versions.
Informs Room that it is allowed to destructively recreate database tables from specific starting schema versions .