I'm trying to fill a JCombobox from items in a multidimensional table.
the items I trying to ad are the names of cities in that table.
this is my code :

```
String t21[][] = {{"Azores","Alaska","Pacific Time US & Canada","Chihuahua, La Paz, Mazatlan - New","Guadalajara, Mexico City, Monterrey - New","Bogota, Lima, Quito, Rio Branco","Atlantic Time","CasaBlanca GMT","Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna","Athens, Bucharest, Istanbul","Moscow, St. Petersburg, Volgograd","Abu Dhabi, Muscat","Chennai, Kolkata, Mumbai, New Delh","Almaty, Novosibirsk","Bangkok, Hanoi, Jakarta","Beijing, Chongqing, Hong Kong, Urumqi","Osaka, Sapporo, Tokyo","Canberra, Melbourne, Sydney","",""},
        {"-6","-5","-4","-3","-2","-1","0","1","2","3","4","5","6","7","8","9","10"}};
for( int i = 0; i< t21.length-1; i++){
                   jComboBox1.addItem(t21[0][i]);
               }

```

but when I run my program I get this error :

> 
> Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
>  at temps.interfac$2.run(interfac.java:125) at
>  java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251) at
>  java.awt.EventQueue.dispatchEventImpl(EventQueue.java:727) at
>  java.awt.EventQueue.access$200(EventQueue.java:103) at
>  java.awt.EventQueue$3.run(EventQueue.java:688) at
>  java.awt.EventQueue$3.run(EventQueue.java:686) at
>  java.security.AccessController.doPrivileged(Native Method) at
>  java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
>  at java.awt.EventQueue.dispatchEvent(EventQueue.java:697) at
>  java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
>  at
>  java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
>  at
>  java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
>  at
>  java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
>  at
>  java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
>  at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
> 
> 
>