No. The line terminating characters may be different in the copy. Sometimes this is a useful feature if you often copy text files between different types of computer.
Here is the loop from the copyFile()
method.
line = source.readLine(); while ( line != null ) { dest.write(line); dest.newLine(); line = source.readLine(); }
Here is the same loop written in a style that is commonly used with the C programming language. This style also works for Java:
while ( (line = source.readLine()) != null ) { dest.write(line); dest.newLine(); }
The key to understanding this is to understand that an assignment statement is an expression and has a value. That value is the value that is assigned to the variable. So this:
(line = source.readLine())
has a value that is non-null after a successful readLine()
and null upon end-of-file.
Say that the file has data in it:
This may be more bother than it is worth, but programmers familiar with C are likely to use this style, so you will see it often.
Will this form of the loop work correctly with an empty file?