What character encoding does ObjectOutputStream 's writeObject method use?

java character-encoding utf-16 fileoutputstream objectoutputstream
bikashg picture bikashg · Dec 8, 2010 · Viewed 8.2k times · Source

I read that Java uses UTF-16 encoding internally. i.e. I understand that if I have like: String var = "जनमत"; then the "जनमत" will be encoded in UTF-16 internally. So, If I dump this variable to some file such as below:

fileOut = new FileOutputStream("output.xyz");
out = new ObjectOutputStream(fileOut);
out.writeObject(var);

will the encoding of the string "जनमत" in the file "output.xyz" be in UTF-16? Also, later on if I want to read from the file "output.xyz" via ObjectInputStream, will I be able to get the UTF-16 representation of the variable?

Thanks.

Answer

Andrzej Doyle picture Andrzej Doyle · Dec 8, 2010

So, If I dump this variable to some file... will the encoding of the string "जनमत" in the file "output.xyz" be in UTF-16?

The encoding of your string in the file will be in whatever format the ObjectOutputStream wants to put it in. You should treat it as a black box that can only be read by an ObjectInputStream. (Seriously - even though the format is IIRC well-documented, if you want to read it with some other tool, you should serialise the object yourself as XML or JSON or whatever.)

Later on if I want to read from the file "output.xyz" via ObjectInputStream, will I be able to get the UTF-16 representation of the variable?

If you read the file with an ObjectInputStream, you'll get a copy of the original object back. This will include a java.lang.String, which is a just stream of characters (not bytes) - from which you could get the UTF-16 representation if you wished via the getBytes() method (though I suspect you don't actually need to).

In conclusion, don't worry too much about the internal details of serialization. If you need to know what's going on, create the file yourself; and if you're just curious, trust in the JVM to do the right thing.

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