Understand the OutOfMemoryError Exception
https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/memleaks002.html
OutOfMemoryError系列（4）: Metaspace - 鐵錨的CSDN博客 - CSDN博客
https://blog.csdn.net/renfufei/article/details/78061354
關於Java.lang.OutOfMemoryError：Metaspace錯誤分析思路 - 換了馬甲的小強的博客 - CSDN博客
https://blog.csdn.net/cockroach02/article/details/52330478
out of memory - java8 "java.lang.OutOfMemoryError: Metaspace" - Stack Overflow
https://stackoverflow.com/questions/36051813/java8-java-lang-outofmemoryerror-metaspace
Permgen space – Plumbr – User Experience & Application Performance Monitoring
https://plumbr.io/outofmemoryerror/permgen-space
Metaspace – Plumbr – User Experience & Application Performance Monitoring
https://plumbr.io/outofmemoryerror/metaspace