How to view the current heap size that an application is using

Question

I think I increased my heap size to 1 GB in NetBeans since I changed the config to look like this   netbeans default options  -J-Xmx1g          After I restarted NetBeans  can I be sure that my app is given 1 GB now   Is there a way to verify this

User · Answer

You can Use the tool   Eclipse Memory Analyzer Tool  http   www eclipse org mat     It is very useful

User · Answer

Personal favourite for when jvisualvm is overkill or you need cli-only  jvmtop  JvmTop 0 8 0 alpha   amd64  8 cpus  Linux 2 6 32-27  load avg 0 12 https   github com patric-r jvmtop  PID MAIN-CLASS      HPCUR HPMAX NHCUR NHMAX    CPU     GC    VM USERNAME    T DL 3370 rapperSimpleApp  165m  455m  109m  176m  0 12   0 00  S6U37 web        21 11272 ver resin Resin  ERROR  Could not attach to VM  27338 WatchdogManager   11m   28m   23m  130m  0 00   0 00  S6U37 web        31 19187 m jvmtop JvmTop   20m 3544m   13m  130m  0 93   0 47  S6U37 web        20 16733 artup Bootstrap  159m  455m  166m  304m  0 12   0 00  S6U37 web        46

User · Answer

public class CheckHeapSize        public static void main String   args               TODO Auto-generated method stub         long heapSize   Runtime getRuntime   totalMemory                 Get maximum size of heap in bytes  The heap cannot grow beyond this size    Any attempt will result in an OutOfMemoryException          long heapMaxSize   Runtime getRuntime   maxMemory                 Get amount of free memory within the heap in bytes  This size will increase    after garbage collection and decrease as new objects are created          long heapFreeSize   Runtime getRuntime   freeMemory              System out println  heapsize  formatSize heapSize            System out println  heapmaxsize  formatSize heapMaxSize            System out println  heapFreesize  formatSize heapFreeSize               public static String formatSize long v            if  v  lt  1024  return v     B           int z    63 - Long numberOfLeadingZeros v     10          return String format    1f  sB    double v    1L  lt  lt   z 10      KMGTPE  charAt z

User · Answer

Attach with jvisualvm from Sun Java 6 JDK   Startup flags are listed

User · Answer

You can use jconsole  standard with most JDKs  to check heap sizes of any java process

User · Answer

You can do it by MXBeans   public class Check       public static void main String   args            MemoryMXBean memBean   ManagementFactory getMemoryMXBean             MemoryUsage heapMemoryUsage   memBean getHeapMemoryUsage             System out println heapMemoryUsage getMax        max memory allowed for jvm -Xmx flag  -1 if isn t specified          System out println heapMemoryUsage getCommitted        given memory to JVM by OS   may fail to reach getMax  if there isn t more memory          System out println heapMemoryUsage getUsed        used now by your heap         System out println heapMemoryUsage getInit        -Xms flag              ------------------ max ------------------------  allowed to be occupied by you from OS  less than xmX due to empty survival space              ------------------ committed -------             now taken from OS             ------------------ used --                       used by your heap            But remember it is equivalent to Runtime getRuntime    took depicted schema from here   memoryMxBean getHeapMemoryUsage   getUsed         lt   gt  runtime totalMemory   - runtime freeMemory   memoryMxBean getHeapMemoryUsage   getCommitted    lt   gt  runtime totalMemory   memoryMxBean getHeapMemoryUsage   getMax          lt   gt  runtime maxMemory     from javaDoc     init - represents the initial amount of memory  in bytes  that the   Java virtual machine requests from the operating system for memory   management during startup  The Java virtual machine may request   additional memory from the operating system and may also release   memory to the system over time  The value of init may be undefined       used - represents the amount of memory currently used  in bytes        committed - represents the amount of memory  in bytes  that is   guaranteed to be available for use by the Java virtual machine  The   amount of committed memory may change over time  increase or   decrease   The Java virtual machine may release memory to the system   and committed could be less than init  committed will always be   greater than or equal to used       max - represents the maximum amount of memory  in bytes  that can be   used for memory management  Its value may be undefined  The maximum   amount of memory may change over time if defined  The amount of used   and committed memory will always be less than or equal to max if max   is defined  A memory allocation may fail if it attempts to increase   the used memory such that used   committed even if used  lt   max would   still be true  for example  when the system is low on virtual memory          ----------------------------------------------                                                                                                                 ----------------------------------------------        --------         init      ---------------             used      ---------------------------                committed      ----------------------------------------------                          max   As additional note  maxMemory is less than -Xmx because there is necessity at least in one empty survival space  which can t be used for heap allocation     also it is worth to to take a look at here and especially here

User · Answer

Use this code      Get current size of heap in bytes long heapSize   Runtime getRuntime   totalMemory         Get maximum size of heap in bytes  The heap cannot grow beyond this size    Any attempt will result in an OutOfMemoryException  long heapMaxSize   Runtime getRuntime   maxMemory         Get amount of free memory within the heap in bytes  This size will increase    after garbage collection and decrease as new objects are created  long heapFreeSize   Runtime getRuntime   freeMemory       It was useful to me to know it

[java] How to view the current heap size that an application is using?

Examples related to java

Examples related to netbeans

Examples related to heap

Examples related to heap-memory