刚把Eclipse中新建的练习项目导入idea的时候想使用lambda表达式发现一直报如下错误：

lambda expressions are not supported at language level '5'

将项目默认sdk替换成jdk8仍然不起作用，最后发现需要修改Source中的languagelevel为8，找到stackoverflow上一个回答不错，copy如下供大家参考：

I had to do a few things to get rid of this problem.

  1. File > Project Structure > Project > Project SDK: Change it to Java 1.8.XX
  2. File > Project Structure > Project > Language Level: SDK 8 (in my case SDK default was already 8)
  3. File > Project Structure > Modules > Sources > SDK 8 (in my case SDK default was already 8)
  4. File > Settings > Build, Execution, Deployment > Compiler > Java Compiler > Project bytecode version > 1.8
  5. File > Settings > Build, Execution, Deployment > Compiler > Java Compiler > Per-module bytecode version > Target bytecode version > 1.8

That should do the trick.