Using Jprofile to discover and fix memory leaks

One of the performance analysis is: When oom occurs, browse object assignments and references to discover and fix memory leaks;

Sample program Pointfactory

 Public classPointfactory {protectedArrayList points =NewArrayList (); protected StaticPointfactory instance =Newpointfactory ();  PublicPoint Createpoint (intXinty) { point point=NewPoint (x, y);  This. Points.Add (point); returnPoint ; }     Public voidRemovepoint (Point point) { This. Points.remove (point); }     Public voidprinttestpoints () { for(inti = 0; I < 5; i++) { point point=Createpoint (i, I); System.out.println ("point =" +Point ); }    }     Public Staticpointfactory getinstance () {returninstance; }     Public Static voidMain (string[] args)throwsException {JFrame frame=NewJFrame ("Points Test");        Frame.setdefaultcloseoperation (Windowconstants.exit_on_close); JButton Button=NewJButton ("Print Test Points"); Button.addactionlistener (NewActionListener () { Public voidactionperformed (ActionEvent e) {pointfactory.getinstance (). printtestpoints ();        }        });        Frame.getcontentpane (). Add (button); Frame.setsize (200, 100); Frame.setvisible (true); }}

View Code

Run pointfactory;

Run Jprofile, select Local JVM;

Select the program;

There was a terrible warning:

In some cases, a bug in attach mode can cause the JVM to crash;

The Sun JVM Attach API is a non-standard set of APIs in the Sun JVM that can be connected to the JVM;

Bug Details:

• Sun Java (HotSpot) client JVM can crash in attach mode due to a JVM bug
  Due to a JVM bug 6776659 HotSpot client JVM can crash in attach mode.
  There is no crash for the server JVM:JVM Option-server solves the problem.

Source Document

Let's just run it in server mode.

This time there was no hint;

Choose

Select Instrumentation Dashboard, we want to see all the analysis;

So many classes, I suspect that the point class has a memory leak, then just look at it, set the view Filters;

There is no point button, so there is no class created;

But the view inside is still empty ah;

I had to use java.awt.Point, but fortunately I was witty;

Why does the 5 class come out total is 333?

Once more, turn 418;

Click Garbage collection Run GC:

10 remaining instances, normal, 10 instances, why there are 418 so many;

And so on, the dot button, Run GC, and total 5 increments per point, proves that the point class is not recoverable;

Already integrated into Eclipse, can profile as Java application, very convenient;

So why didn't the point class release? Clearly it is useless;

The actual project, find source code and then find the reference will be exhausted people, we still through the runtime stack snapshot to see it;

Switch to the heap view;

In the cumulative reference list, you can see who referred to point;

Here is points this ArrayList quoted, but no removal resulted;

Call Removepoint when you are done with it.

Using Jprofile to discover and fix memory leaks