Unknown buffer size to be read from a DataInputStream in java

Question

I have the following statement:

DataInputStream is = new DataInputStream(process.getInputStream());

I would like to print the contents of this input stream but I dont know the size of this stream. How should I read this stream and print it?

Answer 1

It is common to all Streams, that the length is not known in advance. Using a standard InputStream the usual solution is to simply call read until -1 is returned.

But I assume, that you have wrapped a standard InputStream with a DataInputStream for a good reason: To parse binary data. (Note: Scanner is for textual data only.)

The JavaDoc for DataInputStream shows you, that this class has two different ways to indicate EOF - each method either returns -1 or throws an EOFException. A rule of thumb is:

• Every method which is inherited from InputStream uses the "return -1" convention,
• Every method NOT inherited from InputStream throws the EOFException.

If you use readShort for example, read until an exception is thrown, if you use "read()", do so until -1 is returned.

Tip: Be very careful in the beginning and lookup each method you use from DataInputStream - a rule of thumb can break.