注释对android运行时有什么影响？

Question

I like to add...

...    
System.out.println(" *description* "); 
...

... lines to my code blocks for debugging purposes (mostly to catch runtime and logic errors. I usually delete them, but lately I have been just adding "//" before them so that they stay there to prevent having to retype them, slash, to use them as a marker reminding myself that I've already debugged that part.

Is better to delete these "debug println's" rather than adding "//" before them, or if they would both have the same effect on the app runtime ?

Any insights appreciated.

Answer 1

No. By design comments are not used as part of the code (except with certain cases of javadocs appearing in jars).

The compiler which translates the source code into JVM bytecode will simply ignore the comments,

Answer 2

Comments and commented out code have no effect on runtime performance. None whatsoever. (Not even javadoc comments!!)

However, leaving "commented out" debug statements in your code is bad practice because it makes your code a lot harder to read. Obviously, this is not a concern while you are debugging ... but you shouldn't leave them there in the long term.

I recommend two alternatives:

• Replace the println calls with use of a logging framework, and log those things at "debug" level. You need to be a bit careful because logging does have an impact on performance. But there are ways to minimize the impact ... depending on the framework you are using.

• Use your version control history to keep a snapshot of the code with the debug statements active. Then delete them.

See also:

• Commenting out System.out.println