*** old/agent/src/share/classes/sun/jvm/hotspot/tools/HeapSummary.java	Fri Nov  4 13:06:44 2011
--- new/agent/src/share/classes/sun/jvm/hotspot/tools/HeapSummary.java	Fri Nov  4 13:06:44 2011

*** 28,37 ****
--- 28,38 ----
  import sun.jvm.hotspot.gc_interface.*;
  import sun.jvm.hotspot.gc_implementation.g1.*;
  import sun.jvm.hotspot.gc_implementation.parallelScavenge.*;
  import sun.jvm.hotspot.gc_implementation.shared.*;
  import sun.jvm.hotspot.memory.*;
+ import sun.jvm.hotspot.oops.*;
  import sun.jvm.hotspot.runtime.*;
  
  public class HeapSummary extends Tool {
  
     public static void main(String[] args) {

*** 132,141 ****
--- 133,145 ----
           printValMB("free     = ", permFree);
           System.out.println(alignment + (double)permGen.used() * 100.0 / permGen.capacity() + "% used");
        } else {
           throw new RuntimeException("unknown CollectedHeap type : " + heap.getClass());
        }
+ 
+       System.out.println();
+       printInternStringStatistics();
     }
  
     // Helper methods
  
     private void printGCAlgorithm(Map flagMap) {

*** 246,251 ****
--- 250,292 ----
           }
        } else {
           return -1;
        }
     }
+ 
+    private void printInternStringStatistics() {
+       class StringStat implements StringTable.StringVisitor {
+          private int count;
+          private long size;
+          private OopField stringValueField;
+ 
+          StringStat() {
+             VM vm = VM.getVM();
+             SystemDictionary sysDict = vm.getSystemDictionary();
+             InstanceKlass strKlass = sysDict.getStringKlass();
+             // String has a field named 'value' of type 'char[]'.
+             stringValueField = (OopField) strKlass.findField("value", "[C");
+          }
+ 
+          private long stringSize(Instance instance) {
+             // We include String content in size calculation.
+             return instance.getObjectSize() +
+                    stringValueField.getValue(instance).getObjectSize();
+          }
+ 
+          public void visit(Instance str) {
+             count++;
+             size += stringSize(str);
+          }
+ 
+          public void print() {
+             System.out.println(count +
+                   " interned Strings occupying " + size + " bytes.");
+          }
+       }
+ 
+       StringStat stat = new StringStat();
+       StringTable strTable = VM.getVM().getStringTable();
+       strTable.stringsDo(stat);
+       stat.print();
+    }
  }