Java memory usage

[Ben Field]

Hi There - how can I find out how much memory a java object uses?

It is a collection of hashmaps with various other objects referenced and I need to know the total memory usage - are there any jvm tools for thsis?

Thanks
Ben

[Max Habibi]

   public static void main(String args[])
   {
Runtime r = Runtime.getRuntime();
 
long start = r.freeMemory();
 
Map map = new TreeMap();
 
for (int i=0; i<1000;i++)
{
map.put(new String("key") + i ,new String("value"));
 
}
long end = r.freeMemory();
System.out.println("start=:"+start);
System.out.println("end=:"+end);
 
long memoryUsed = start - end;
System.out.println("memoryUsed=:"+memoryUsed);
 

 
   }

[Ben Field]

Thanks you very much!