A lot of times I'll see code like this:

...
s = reader.readLine();
... //many lines that use s


If your method is very small, this is ok, but if it's a long method where s is used for many lines, this code becomes difficult to understand. The
next person that looks at this code will be forced to look at the instantiation of s to figure out what it represents.
It's better to give your temporary variable a descriptive name in that situation:


...
line = reader.readLine();
... //many lines that use line


Or better yet:


...
logLine = logReader.readLine();
... //many lines that use logLine