I want to store multiple values (String, Int and Date) in a file via Java in Android Studio.
I don't have that much experience in that area, so I tried to google a bit, but I didn't get the solution, which I've been looking for. So, maybe you can recommend me something?
What I've tried so far:
Android offers a SharedPreferences feature, which allows a user to save a primitive value for a key. But I have multiple values for a key, so that won't work for me.
Another option is saving data on an external storage medium as file. As far as good. But I want to keep the filesize at minimum and load the file as fast as possible. That's the place, where I can't get ahead. If I directly save all values as simple text, I would need to parse the .txt file per hand to load the data which will take time for multiple entries.
Is there a possibility to save multiple entries with multiple values for a particular key in an efficient way?
No need to reinvent a bicycle. Most probably the best option for your case is using the databases. Look into Sqlite or Realm.
You don’t divulge enough details about your data structure or volume, so it is difficult to give a specific solution.
Generally speaking, you have these three choices.
Serialize a collection
I have multiple values for a key
You could use a Map with a List or Set as its value. This has been discussed countless times on Stack Overflow.
Then use Serialization to write and read to storage.
Text file
Write a text file.
Use Tab-delimited or CSV format if appropriate. I suggest using the Apache Commons CSV library for that.
Database
If you have much data, or concurrency issues with multiple threads, use a database such as the H2 Database Engine.
Related
How to write Rowloader JAVA code to inject data from sample.csv file into GenfireXD database.
The GemFireXD distribution includes a JDBCRowLoader source example. Look in the examples directory. In your case you will have to determine which field of your CSV you want to consider as primary keys, parse the CSV and return rows as needed.
You can check IMPORT_DATA_EX and IMPORT_TABLE_EX procedures to load data into GemFireXD.
Since you mentioned csv format IMPORT_DATA_EX might be the recommend way to do it since you can also tweak the number of threads and constraints while loading the data. It's definitely one of the fastest ways to do it but please note that the csv file but be available from the node you're issuing the command.
You might also want to consider starting a peer member with host-data=false.
Reference: http://gemfirexd.docs.pivotal.io/latest/userguide/index.html#reference/system_procedures/derby/rrefimportdataproc_ex.html
So I am working on a GAE project. I need to look up cities, Country Names and Country Codes for sign ups, LBS, ect ...
Now I figured that putting all the information in the Datastore is rather stupid as it will be used quite frequently and its gonna eat up my datastore quotations for no reason, specially that these lists arent going to change, so its pointless to put in datastore.
Now that leaves me with a few options:
API - No budget for paid services, free ones are not exactly reliable.
Upload Parse-able file - Favorable option as I like the certainty that the data will always be there.
So I got the files needed from GeoNames (link has source files for all countries in case someone needs it). The file for each country is a regular UTF-8 tab delimited file which is great.
However, now that I have the option to choose how to format and access the data, the question is:
What is the best way to format and retrieve data systematically from a static file in a Java servelet container ?
The best way being the fastest, and least resource hungry method.
Valid options:
TXT file, tab delimited
XML file Static
Java Class with Tons of enums
I know that importing country files as Java Enums and going through their values will be very fast, but do you think this is going to affect memory beyond reasonable limits ? On the other hand, every time I need to access a record, the loop will go through a few thousand lines until it finds the required record ... reading line by line so no memory issues, but incredibly slow ... I have had some experience with parsing an excel file in a Java servelet and it took something like 20 seconds just to parse 250 records, on large scale, response time WILL timeout (no doubt about it) so is XML anything like excel ??
Thank you very much guys !! Please provide opinions, all and anything is appreciated !
Easiest and fastest way would be to have the file as a static web resource file, under the WEB-INF folder and on application startup, have a context listener to load the file into memory.
In memory, it should be a Map, mapping from a key you want to search by. This will allow you like a constant access time.
Memory consumption would only matter if it is really big. A hundred thousand record for example not worth optimizing if you need to access this many times.
The static file should be plain text format or CSV, they are read and parsed most efficiently. No need XML formatting as parsing it would be slow.
If the list is really big, you can break it up into multiple, smaller files, and only parse those and only when they are required. A reasonable, easy partitioning would be to break it up by country, but any other partitioning would work (like based on its name using the first few characters from its name).
You could also consider building this Map in the memory once, and then serialize this map to a binary file, and include that binary file as a static resource file, and that way you would only have to deserialize this Map and would be no need to parse/process it as a text file and build objects yourself.
Improvements on the data file
An alternative to having the static resource file as a text/CSV file or a serialized Map
data file would be to have it as a binary data file where you could create your own custom file format.
Using DataOutputStream you can write data to a binary file in a very compact and efficient way. Then you could use DataInputStream to load data from this custom file.
This solution has the advantages that the file could be much less (compared to plain text / CSV / serialized Map), and loading it would be much faster (because DataInputStream doesn't use number parsing from a text for example, it reads the bytes of a number directly).
Hold the data in source form as XML. At start of day, or when it changes, read it into memory: that's the only time you incur the parsing cost. There are then two main options:
(a) your in-memory form is still an XML tree, and you use XPath/XQuery to query it.
(b) your in-memory form is something like a java HashMap
If the data is very simple then (b) is probably best, but it only allows you to do one kind of query, which is hard-coded. If the data is more complex or you have a variety of possible queries, then (a) is more flexible.
I am designing a e-Diary application in which the user can store textual data EVERY DAY.
I thought of using a database but now I am looking for other alternatives , thought of encrypted files , but what if they get deleted ?
Could someone provide me ways of doing this.
BTW, I am using Java.(If this is important).
EDIT: Currently I am using files for acheiving this, for login I am using a file in which the username, password are stored in the format username:password, This is not a good approach, so I am looking for some secure approaches.
Serialize your Data and store it using flatfiles.
But why dont you want to use SQlite?
Serializing and storing to the disk is a database aswell.
If you want to serialize it there are a few tutorials and code examples around.
check How to serialize an object into a string
for example.
If you want to use a proper database (which is recommend!) you may check different databases and examples at Java and SQLite
I plan on reading several files when my app/game is created and using the information from them for the entirety of the app. I also have to write to the file at one point.
I have two files. One is a 2-column text file that I'll turn into a dictionary for fast searching. The other is a text file that has 11 columns. I'll make a dictionary out of two of the columns, and the other data I need kept as is so I can write to the columns to count the amount of times something happens in different circumstances for datamining.
Currently, I've turned the second file into a list of a list of strings, or List>. I can't figure out how to pass that around in intents. ".putStringArrayListExtra" only works for a list of strings.
Am I going about this the wrong way entirely? This is my first real Android app.
In order to store a data structure into an Intent, it has to be either serializable or parcelable. If your data structure is neither of them, you might create a class that would implement Serializable and manage it. A good example might be found here.
Once done, you then might use Intent.putSerializable(...) to store your data structure. See this:
Using putSerializable in Android
Additionally to this, if you could convert your structure into a JSON structure, you'd already have it done since it would be treated as a String. If not, the above solution should be easy to do.
I've made an Android application which contains most used German words and sentences. The application contains a CSV file which stores all the data.
Currently it is working as expected but I want to ask if there is a better way to store such data directly in the app?
I'm also thinking about the ability to update the data via internet like adding new words and sentences.
Thanks!
Miretz
If you want to modify the content (update, remove etc.) I would suggest using SQLite DB which has a pretty nice built-in integration with the Android platform.
There are 2 types SQLDatabaseLite and SharedPreference. Major difference between both is that one is organized and the other not so.
If you need a quick use of a storage facility within your app for example changing text sizes between activity SharedPrefference works best for you.
If you have a complex database system where you need more than one data to be saved for a particular event SQLDatabaseLite is for you example of this is spreadsheet of data for customers; Name, Phone Number, etc.