Thread: data and object streams

hi all,

java newbie here - reading through the java tutorials and a little confused here.

i've read that using a data stream means that the values are represented in an internal binary format. does this mean if you use a data stream to output some int values to a file, you won't be able to read the data in the file?

let's say you want to output some int values to a .txt file: 5, 10, and 25.

Why would you use a data stream and not a byte or character stream?

also, can anyone provide a simple explanation of an object stream and an example of when you would use it?

won't be able to read the data in the file

You can read the data with a data stream. The data written will NOT be ASCII text.

want to output some int values to a .txt file: 5, 10, and 25.

What format/representation for the data do you want in the .txt file? I would assume you'd want ASCII characters in a .txt file. To get those you need to write Strings.

Originally Posted by bbr201

also, can anyone provide a simple explanation of an object stream and an example of when you would use it?

Object streams allow you to save an object. An example might be for a program to save some internal state to be opened up at a later time, in the simplest case it can save one or more user preferences, in more complex cases save session and data values in J2EE web applications. The class must implement Serializable to be able to be saved in this manner.

Originally Posted by Norm

What format/representation for the data do you want in the .txt file? I would assume you'd want ASCII characters in a .txt file. To get those you need to write Strings.

What advantage is there to using a data stream to output and read primitive data types?

In the case of a text file, it makes sense that you would want ASCII characters in the event that a human being wants to open the file and see the contents. So I assume in this case it would be best to work with a character stream.

But why ever choose the data stream then?

In other words, let's say you use another file to read and store values 'data.dat'. No human being will ever need to open the file and see the contents. It is only used by a program to store (and later read) int values. In this case, couldn't you use a byte, character, or data stream? How would you choose which to use?

I guess I am just confused in general. :-(