I have a code base and some methods are never used.
Does javac remove the unused methods from the class file?
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.
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).
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