PersistenceMigrationsSample/app/src/room/java/com/example/android/persistence/migrations/UserRepository.java [51:72]:
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                final LoadUserCallback userCallback = loadUserCallback.get();
                if (userCallback == null) {
                    return;
                }
                if (user == null) {
                    userCallback.onDataNotAvailable();
                } else {
                    mCachedUser = user;
                    userCallback.onUserLoaded(mCachedUser);
                }
            });
        });
    }

    /**
     * Insert an new user or update the name of the user.
     *
     * @param userName the user name
     * @param callback callback that gets triggered when the user was updated.
     */
    void updateUserName(String userName, UpdateUserCallback callback) {
        final WeakReference<UpdateUserCallback> updateUserCallback = new WeakReference<>(callback);
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PersistenceMigrationsSample/app/src/room3/java/com/example/android/persistence/migrations/UserRepository.java [56:79]:
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                        final LoadUserCallback userCallback = loadUserCallback.get();
                        if (userCallback == null) {
                            return;
                        }
                        if (user == null) {
                            userCallback.onDataNotAvailable();
                        } else {
                            mCachedUser = user;
                            userCallback.onUserLoaded(mCachedUser);
                        }
                    }
                });
            }
        });
    }

    /**
     * Insert an new user or update the name of the user.
     *
     * @param userName the user name
     * @param callback callback that gets triggered when the user was updated.
     */
    void updateUserName(String userName, UpdateUserCallback callback) {
        final WeakReference<UpdateUserCallback> updateUserCallback = new WeakReference<>(callback);
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