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addin two matrices.no display in final cell in the result table:java.lang.NullPointerException error

 
Kelvin Williams
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Campbell Ritchie
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Welcome to the Ranch

Where do you get the exception? Which refrernce is null? Please post the exact exception message.
 
Kelvin Williams
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Campbell Ritchie wrote:Welcome to the Ranch

Where do you get the exception? Which refrernce is null? Please post the exact exception message.


Apparently my error is at line 118. I get these lines of errors from Netbeans:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at MatrixApp.matrixAddition(MatrixApp.java:526) //this is in reference to line 118
at MatrixApp.matBNextActionPerformed(MatrixApp.java:483)
at MatrixApp.access$600(MatrixApp.java:11)
at MatrixApp$7.actionPerformed(MatrixApp.java:273)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2713)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:680)
at java.awt.EventQueue$4.run(EventQueue.java:678)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
 
Campbell Ritchie
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Break that line 118 up into lots of different parts. Two ints, made from two Strings, taken from two table models, which have values at (i, j). Break it into at least 6 parts, maybe 8 parts, because any of those reference types might be null. You don’t yet know which.
Adding the two ints can’t cause NUllPointerException (NPE), but if any of the other parts of the equation is null, that will cause the NPE. Start by seeing which new line number the NPE is associated with. Then put some test code in, like this:-
 
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