구차니의 잡동사니 모음

*/5

3-59/5

# jcmd 10776 help
10776:
The following commands are available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
VM.classloader_stats
GC.rotate_log
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.finalizer_info
GC.heap_info
GC.run_finalization
GC.run
VM.uptime
VM.dynlibs
VM.flags
VM.system_properties
VM.command_line
VM.version
help

For more information about a specific command use 'help 

# jcmd 10776 GC.heap_info
10776:
 PSYoungGen      total 192512K, used 187956K [0x00000000ec400000, 0x00000000f8300000, 0x0000000100000000)
  eden space 189952K, 98% used [0x00000000ec400000,0x00000000f7a0d258,0x00000000f7d80000)
  from space 2560K, 60% used [0x00000000f7d80000,0x00000000f7f00000,0x00000000f8000000)
  to   space 2560K, 0% used [0x00000000f8080000,0x00000000f8080000,0x00000000f8300000)
 ParOldGen       total 647168K, used 591782K [0x00000000c4c00000, 0x00000000ec400000, 0x00000000ec400000)
  object space 647168K, 91% used [0x00000000c4c00000,0x00000000e8de99b8,0x00000000ec400000)
 Metaspace       used 107438K, capacity 109826K, committed 110336K, reserved 1146880K
  class space    used 13031K, capacity 13457K, committed 13568K, reserved 1048576K

Element Type        Encoding
boolean             Z
byte                B
char                C
class or interface  Lclassname;
double              D
float               F
int                 I
long                J
short               S 

it is an array of objects as specified by JVM Specifications for internal representation of class names:

• a single [ means an array of
• L followed by a fully qualified class name (e.g. java/lang/Object) is the class name terminated by semicolon ;

so [Ljava.lang.object; means Object[]