How do I read this line in a Java stack trace?

Question

The stack is complicated with the involvement of lambda (note that the line number is lost due to obsfucation). What does " access$lambda$12" actually mean and is there a way to locate this in the code without knowing the actual line number?

at com.group.RKGroup.com.my.MyClass access$lambda$12(com.group.RKGroup,int,com.my.PType) (RKGroup.java:43324)

The line number is useless because this stack trace was obsfucated with Proguard.

This denotes a lambda declared in your `access` method. Possibly the 12th one in the method .... though I wouldn't swear to that. — Stephen C, Feb 22 '18 at 14:06
Possible duplicate of [What is the $1 in class file names?](https://stackoverflow.com/questions/1075207/what-is-the-1-in-class-file-names) — phflack, Feb 22 '18 at 14:13
@Eran: the line number is useless because this stack trace was obsfucated with Proguard. — user1615898, Feb 22 '18 at 14:13
Always help may come for the caller (the next line) of that lambda. The source does not really have a line number 43324, I pray? — Joop Eggen, Feb 22 '18 at 14:24

score 3 · Answer 1 · answered Feb 22 '18 at 14:14

Under normal circumstances, that would denotes a lambda declared in a method called access. Possibly the 12th lambda in the method .... though I wouldn't swear to that.

Note that the line number is lost due to obfuscation.

OK that explains how you got void [sic] as a class name. But it also means that the method name could be bogus too.

The only you are going to be sure what this line is referring to is to attempt to reverse engineer the bytecodes.

At this point, I would recommend that you send the stacktrace to the vendor of this software, and get them to help you. If they can't or won't, ask for access to the source code. If they can't or won't give you access, look for a new product. Debugging someone elses obfuscated code is a nightmare.

score 1 · Accepted Answer · answered Feb 22 '18 at 20:23

That looks like lambda inside a method, but...

javac does not generate such names (close to that, but not that). javac (even if this is never specified) generates them as

lambda$<method-name-where-used>$<incremental-number>

Or if you have something like this:

List<Integer> r = Stream.of(1).map(x -> x).collect(Collectors.toList());
lambda$new$<incremental-number>

Notice that in your case the method name (access) comes first, so this looks very much like retro-lambda for android. IIRC they generate code like this, which is again un-specified, but what it really means that there is a lambda expression in your access method, specifically the 12-th lambda in that method. Again, IIRC, retro-lambda uses same incremental-per-method naming.

How do I read this line in a Java stack trace?

2 Answers2