try these:
 1) type:(note! Please set two breakpiont
according to the comments)
public class Test {
	  int x;
	  {
	    x =1;
	    System.out.println(0);
	  }
	  Test() {
	    super();
	  }
	  Test(int x) {
	    this.x = x;// breakpoint here
	    System.out.println(2);
	  }
	  public static void main(String[] args) {
	    new Test(2); // breakpoint here
	  }
     }
     
2) copy below contents from anywhere     
    class Z {
	  static int peek() { 
	    return j; 
	  }
	  static int i = peek();
	  static int j = 1;
	}
	
	public class Test {
	  public static void main(String[] args) {
	    int i = Z.i;// breakpoint here
	    System.out.println(i);
	  }
	}	

3)In src editor, mouse select the entire lines of
class Test(typed in step 1 above)
4)paste the already copy content
5)In Glyph and Line number Margin, there are two
breakpoints piled up.
6)Click it.
A javax.jmi.reflect.InvalidObjectException
exception has occurred.
However, the system should continue working
without further problems.
Click Details for the stack trace:
javax.jmi.reflect.InvalidObjectException: Object
with MOFID
874097E4-FB1D-11D8-A067-57A74E49AA77:0000000000000F89
no longer exists.
	at
org.netbeans.mdr.handlers.BaseObjectHandler._getDelegate(BaseObjectHandler.java:322)
	at
org.netbeans.mdr.handlers.InstanceHandler.getInstanceDelegate(InstanceHandler.java:48)
	at
org.netbeans.mdr.handlers.InstanceHandler._immediateComposite(InstanceHandler.java:251)
	at
org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement._immediateComposite(MetadataElement.java:1315)
	at
org.netbeans.mdr.handlers.InstanceHandler.refImmediateComposite(InstanceHandler.java:243)
	at
org.netbeans.modules.javacore.jmiimpl.javamodel.MetadataElement.getResource(MetadataElement.java:457)
	at
org.netbeans.jmi.javamodel.Field$Impl.getResource(Unknown
Source)
	at
org.netbeans.modules.java.ui.NavigationView.selectNodeImpl(NavigationView.java:325)
	at
org.netbeans.modules.java.ui.NavigationView.access$100(NavigationView.java:63)
	at
org.netbeans.modules.java.ui.NavigationView$2.run(NavigationView.java:309)
	at org.openide.util.Task.run(Task.java:136)
	at
org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:330)
[catch] at
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:686)

7)repeat 1)-6) exceptions not throw again.