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javafileoutputstreamfilewriterdataoutputstream
Paradox
Paradox

Reputation: 353

Java Input and Output

Explain the difference between the outputs of the following two fragments of code for outputting an int i to a file:

i)

PrintWriter outfile = new PrintWriter(new FileWriter("ints.txt"));
outfile.print(i);

ii)

DataOutputStream out = new DataOutputStream(new FileOutputStream("ints.dat"));
out.writeInt(i);

I think the Printer writer takes a string and tranforms it into a stream of unicode characters, whereas dataoutput stream converts the data items to sequence of bytes.

What more would you add?

Upvotes: 0

Views: 310

Answers (3)

Liv
Liv

Reputation: 6124

possibly repeating what was already said, but just to make it more explicit:

when you use a printwriter, and say you have an int value of 65 -- the print writer will print 2 characters: '6' and '5'

when you use an outputstream, this prints bytes so it will write to the file a byte with the value of 65 -- this happens to be the character code in ASCII/UTF-8 for 'A' so if you open up the file in a text editor you will see an "A" character -- rather than '6' followed by '5' as above.

Upvotes: 0

MarcoS
MarcoS

Reputation: 13564

From DataOutputStream javadoc:

A data output stream lets an application write primitive Java data types to an output stream in a portable way. An application can then use a data input stream to read the data back in.

From PrintWriter javadoc

Prints formatted representations of objects to a text-output stream.

Everything is just bytes, but they represent different things. With a DataOutpuStream you get bytes that you can read back directly to your primitive Java type int, whereas with a PrintWriter you don't.

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533432

Files only contain byte, so it all ends up as bytes in the end.

A String is already a stream of characters. When you write a String to a file it has to turn it into a stream of bytes.

An int is four bytes. writeInt() turns it into a big endian number.

Upvotes: 1

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