Question

I am looking at the code on page 11 here http://www.cs.usfca.edu/~parrt/doc/java/JavaIO-notes.pdf

I have trouble with one statement. I thought the result of an assignment was an lvalue. So ((byteRead = inFile.read()) != -1) should be the same as (inFile.read()) != -1). This doesn’t seem to be the case though looking at the output. So my question is how is the statement ((byteRead = inFile.read()) != -1) parsed?

EDIT: It seems from the responses that I had the current interpretation of the result of an assignment. I was wondering what goes wrong by replacing the code fragment

int byteRead;

while((byteRead = inFile.read()) != -1)

outFile.write(byteRead);

with

while( inFile.read() != -1)

outFile.write( inFile.read());

Answer 1

So, now that you posted both versions of code, the answer is clear:

In your first version, each byte read is assigned to byteRead and then written to the output stream.

In the second version, you consume a byte with the read() but don’t assign it to a variable. Then, you read another byte (the next one in the stream) which you write to the output stream.

So, if the input file is:

abcdefghijklmnopqrstuvwxyz

The output of the first version will be :

abcdefghijklmnopqrstuvwxyz

The output of the second will be :

bdfhjlnqrtuxz