Tutorial Addendum on JVM - Anamnesis Administration

31 December 18:00

Overview

Generally, a new s/computers-and-technology/jvm-list/' onMouseOver="tip('infobox1')" onMouseOut="untip()"> JVM is using the afterward rules to administer memory:

When a JVM is invoked to run an application, it will ask the operating arrangement


for abundant anamnesis to run the JVM itself and some chargeless anamnesis for the application


to make new objects.

When a new item is created, the JVM will admeasure anamnesis for that item out

of the chargeless anamnesis area.

When the chargeless anamnesis breadth is accepting too small, the JVM will ask the operating

system for more.

When a item is no best acclimated by the application, it will be destroyed. Its

memory will be freed up and alloyed aback to the chargeless anamnesis area.

When the chargeless anamnesis breadth is acclimated up, and there is no added added memory


available from the operating system, the JVM will stop the appliance and issue


the "Out of anamnesis error".

Out of Anamnesis Error

I wrote the afterward program to try to advance JVM for added anamnesis in a loop:

 

    /**

    
 * MemoryCrash.java

    
 * Absorb (c) 2002 by Dr.  Yang

    
 */

    
class MemoryCrash {

    
   accessible changeless abandoned main(String[] a) {

    
      int max = 100;

    
      Runtime rt = Runtime.getRuntime();

    
      Object[] arr =  new  Object[max];

    
      for (int n=0; n<max; n++) {

    
         System.out.println("Having "+n*10+" MB and abacus 10 MB...");

    
         arr[n] =  new  long[10*1024*128];

    
         System.out.println(" Chargeless memory: " + rt.freeMemory());

    
         System.out.println("Total memory: " + rt.totalMemory());

    
      	 try {

    
      	    Thread.sleep(2*1000);

    
      	 } bolt (InterruptedException e) {

    
            System.out.println("Interreupted...");

    
      	 }

    
      }

    
   }

    
}