垃圾收集算法：分代收集、复制、标记整理、标记清除
Serial收集器(-XX:+UseSerialGC -XX:+UseSerialOldGC)
Parallel Scavenge收集器(-XX:+UseParallelGC -XX:+UseParallelOldGC)
CMS收集器(-XX:+UseConcMarkSweepGC)
G1(-XX:+UseG1GC)
https://www.oracle.com/java/technologies/java-se-support-roadmap.html
