问题
I have a code base and some methods are never used.
Does javac remove the unused methods from the class file?
回答1:
Q: I want to know if I have a code base and some methods are never used. Does javac remove the unused methods from the class file?
A: No. What goes into the class, stays in the class file.
... however ...
The JVM loads only what's needed into memory. RAM isn't "wasted" on unused classes.
回答2:
No, it doesn't. To verify this, you can run
javap -c foo.bar.MyClass
and see all the code there. You can also access it via reflection (assuming you're running with appropriate permissions).
回答3:
No it doesn't and it can't. Think about what would happen if the compiler did that when you compile a library. All methods that the library wants to export for users, but doesn't use itself would be removed. And there is no way in Java to distinguish between something that is a library and your code.
来源：https://stackoverflow.com/questions/9610163/does-javac-removes-methods-that-are-not-referenced-in-the-code