“从内部类访问变量需要声明为final”错误

Question

I've got this error while trying to use a local member of one class in inner class inside. I know that declare it as final will solve the issue but I read that Java 8 should handle it automaticlly, I'm using Intellij with Java 8 and it still does not compile. Is there any other way to fix it without declare it as final? thanks.

Answer 1

I know that declare it as final will solve the issue but I read that Java 8 should handle it automatically.

Java 8 will handle it if the variable is effectively final .

I can think of two possible explanations:

1. Maybe the variable is not effectively final . Try explicitly declaring it as final . If you get a compilation error (eg saying that something is trying to modify the final ) then the variable isn't effectively final.

2. Maybe you haven't configured Intellij and the project properly for Java 8; eg

   • Set the source level; see @saman's answer
   • Check you have the right JDK selected: Java 8 doesn't compile on Intellij15

Answer 2

I think you should change your language level from "Project Structure" -> "Module" -> "your project name" -> "Source" -> "Language Level" and set it to 8