JVM 垃圾回收 Minor gc vs Major gc vs Full gc

   关于垃圾回收机制及比较请参见：http://colobu.com/2015/04/07/minor-gc-vs-major-gc-vs-full-gc/

   http://colobu.com/2014/12/16/java-jvm-memory-model-and-garbage-collection-monitoring-tuning/