help------about查看ide的版本：
IntelliJ IDEA 2017.3.7 (Ultimate Edition)
Build #IU-173.4710.11, built on April 4, 2019
Licensed to Rover12421 / Rover12421
You have a perpetual fallback license for this version
Subscription is active until December 31, 2099
JRE: 1.8.0_152-release-1024-b18 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 7 6.1
新建的一個maven項目，一路點next創建的，結果 new KafkaProducer<>的時候報錯：
Diamond types are not supported at this language level
可以看到Diamond 是JDK1.7的特性，所以1.5肯定是不支持的。
右鍵項目，選擇Open Module Setting
打開如下的彈窗，報錯就是這里的Language level默認還是5.0
