Viewing the Heap Snapshot

The memory monitor elements are as follows:

memory panel - At the top of the window you see a grid of rectangles representing memory blocks. This is the memory panel. The key on the top right indicates the meaning of each graphical image. For example, blocks that are completely black are at 100% utilization. Clicking a single block opens a dialog showing all the objects in that block.

loaded classes - A list of loaded classes is displayed in the lower-left corner. Choosing a class from the list causes the location of all objects in the class to be displayed in class objects list immediately to the right.

class objects - The class objects list is populated when you select a class from the list of loaded classes. Select an object to see the class details. These include the address of the object, its type, and all references to and from the object. If the object is live, the “Show path from the root” button is enabled. Clicking this button opens the Path from the Root window, which displays dependencies that prevent this object from being garbage collected.

statistics - At the bottom right of the Memory Observer window, click the Statistics button to see a table showing the information for each class. Some objects are internal to the virtual machine. For each class, you see the Object number, size of all objects in the heap, the average size of the object, the percentage of the heap used by the selected class, the percentage of objects live in the selected class, and the percentage of objects that are in the old generation.

See Virtual Machine Memory Profiler (Java Heap Memory Observe Tool) and Running the Java Heap Memory Observe Tool