jvm 1.8 默认的垃圾回收器

Java -XX:+PrintCommandLineFlags -version 查看JVM默认参数

-XX:InitialHeapSize=265695040 
-XX:MaxHeapSize=4251120640 
-XX:+PrintCommandLineFlags 
-XX:+UseCompressedClassPointers 
-XX:+UseCompressedOops
-XX:-UseLargePagesIndividualAllocation 
-XX:+UseParallelGC
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)

+UseParallelGC = 新生代ParallelScavenge + 老年代ParallelOld
+UseParallelOldGC = 同上
-UseParallelOldGC = 新生代ParallelScavenge + 老年代SerialOld

java -XX:+PrintGCDetails -version 查看JVM详细信息

java version "1.8.0_161"
	Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
	Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)
	Heap
	 PSYoungGen      total 75776K, used 2601K [0x000000076b800000, 0x0000000770c80000, 0x00000007c0000000)
	  eden space 65024K, 4% used [0x000000076b800000,0x000000076ba8a558,0x000000076f780000)
	  from space 10752K, 0% used [0x0000000770200000,0x0000000770200000,0x0000000770c80000)
	  to   space 10752K, 0% used [0x000000076f780000,0x000000076f780000,0x0000000770200000)
	 ParOldGen       total 173568K, used 0K [0x00000006c2800000, 0x00000006cd180000, 0x000000076b800000)
	  object space 173568K, 0% used [0x00000006c2800000,0x00000006c2800000,0x00000006cd180000)
	 Metaspace       used 2349K, capacity 4480K, committed 4480K, reserved 1056768K
  class space    used 254K, capacity 384K, committed 384K, reserved 1048576K