jvm 垃圾收集器（Epsilon）
Epsilon不回收内存，只负责堆的管理与布局，对象的分配，与解释器、编译器、监控子系统的协作；
epsilon适合运行时间短、在内存耗尽前就可退出的应用程序
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相关参数：
-XX:+UnlockExperimentalVMOptions：垃圾收集器Epsilon仍处于试验阶段，需使用此参数才可使用Epsilon
-XX:+UseEpsilonGC：使用垃圾收集器Epsilon
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示例
public class Test {
public static void main(String[] args){
byte[] b=new byte[10];
b=null;
System.gc();
}
}
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虚拟机参数
-Xms20m -Xmx20m -Xlog:gc* -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC**********************
控制台输出
[0.007s][warning][gc] Consider enabling -XX:+AlwaysPreTouch to avoid memory commit hiccups
[0.024s][info ][gc,heap,coops] Heap address: 0x00000000fec00000, size: 20 MB, Compressed Oops mode: 32-bit
[0.024s][info ][gc ] Non-resizeable heap; start/max: 20M
[0.024s][info ][gc ] Using TLAB allocation; max: 4096K
[0.024s][info ][gc ] Elastic TLABs enabled; elasticity: 1.10x
[0.024s][info ][gc ] Elastic TLABs decay enabled; decay time: 1000ms
[0.024s][info ][gc ] Using Epsilon
[0.097s][info ][gc ] Heap: 20480K reserved, 20480K (100.00%) committed, 1113K (5.44%) used
[0.098s][info ][gc,metaspace ] Metaspace: 1032M reserved, 4864K (0.46%) committed, 366K (0.03%) used
[0.152s][info ][gc ] GC request for "System.gc()" is ignored
//忽略垃圾回收请求，不进行垃圾回收
[0.153s][info ][gc,heap,exit ] Heap
[0.153s][info ][gc,heap,exit ] Epsilon Heap
[0.153s][info ][gc,heap,exit ] Allocation space:
[0.153s][info ][gc,heap,exit ] space 20480K, 9% used [0x00000000fec00000, 0x00000000fedcf4b0, 0x0000000100000000)
[0.153s][info ][gc,heap,exit ] Metaspace used 717K, capacity 4534K, committed 4864K, reserved 1056768K
[0.153s][info ][gc,heap,exit ] class space used 65K, capacity 403K, committed 512K, reserved 1048576K
[0.153s][info ][gc ] Heap: 20480K reserved, 20480K (100.00%) committed, 1853K (9.05%) used
[0.153s][info ][gc,metaspace ] Metaspace: 1032M reserved, 4864K (0.46%) committed, 717K (0.07%) used
