Following is a short summary of the enhancements to JPDA that have been added in Java SE 6. The documentation for these features is available in the JDI Specification.
Not shown here are the equivalent commands in JDWP. The documentation for these features is available in the JDWP Specification.
New methods:
          VirtualMachine:
           boolean canGetInstanceInfo();       
           long[] instanceCounts(List<?extends ReferenceType?> refTypes);
         ReferenceType:
           List<ObjectReference> instances(long maxInstances);
         ObjectReference:
           List<ObjectReference> referringObjects(long maxReferrers);
New methods:
         
        VirtualMachine:
           boolean canGetClassFileVersion();
           boolean canGetConstantPool();
         ReferenceType:
           int majorVersion();
           int minorVersion();
           int constantPoolCount();
           byte[] constantPool();
New methods:
          VirtualMachine:
            boolean canUseSourceNameFilters();
          ClassPrepareRequest:
            void addSourceNameFilter(String sourceNamePattern);
New methods:
         StackFrame:
           List<Value> getArgumentValues();
New methods:
         VirtualMachine:
           boolean canGetMethodReturnValues();
         MethodExitEvent: 
           Value returnValue();
New methods:
         VirtualMachine:
           boolean canForceEarlyReturn();     
         ThreadReference:
           void forceEarlyReturn(Value value) throws InvalidTypeException, 
                                              ClassNotLoadedException,
                                              IncompatibleThreadStateException;
New methods:
         VirtualMachine
           boolean canRequestMonitorEvents();
         EventRequestManager:
           List<MonitorContendedEnterRequest> monitorContendedEnterRequests();
           List<MonitorContendedEnteredRequest> monitorContendedEnteredRequests();
           List<MonitorWaitRequest> monitorWaitRequests();
           List<MonitorWaitedRequest> monitorWaitedRequests();
New classes:
       public interface MonitorContendedEnterRequest extends EventRequest
         public interface MonitorContendedEnteredRequest extends EventRequest
         public interface MonitorWaitRequest extends EventRequest
         public interface MonitorWaitedRequest extends EventRequest
         public interface MonitorContendedEnterEvent extends LocatableEvent 
         public interface MonitorContendedEnteredEvent extends LocatableEvent 
         public interface MonitorWaitEvent extends LocatableEvent 
         public interface MonitorWaitedEvent extends LocatableEvent 
New methods:
         VirtualMachine
           boolean canGetMonitorFrameInfo();
       
         ThreadReference
           List<MonitorInfo> ownedMonitorsAndFrames()
                           throws IncompatibleThreadStateException;
New classes:
       
         public interface MonitorInfo extends Mirror
New Connector:
com.sun.tools.jdi.ProcessAttach, with arguments
pid and timeout. This allows a debugger
to attach to a debuggee started in debug mode via process id
instead of transport address.