java - JComboBox に多次元テーブルの項目を入力します

Question

多次元テーブルのアイテムから JCombobox を埋めようとしています。私が広告しようとしている項目は、そのテーブルの都市の名前です。これは私のコードです:

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]);
               }

しかし、プログラムを実行すると、次のエラーが発生します。

スレッド「AWT-EventQueue-0」での例外 java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251) の temps.interfac$2.run(interfac.java:125) で java.lang.NullPointerException java.awt で.EventQueue.dispatchEventImpl(EventQueue.java:727) で java.awt.EventQueue.access$200(EventQueue.java:103) で java.awt.EventQueue$3.run(EventQueue.java:688) で java.awt.EventQueue$3 .run(EventQueue.java:686) で java.security.AccessController.doPrivileged(Native Method) で java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) で java.awt.EventQueue.dispatchEvent(EventQueue.java: 697) java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242) で java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161) で java.awt.java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146) の EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150) java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138) の java.awt.EventDispatchThread.run(EventDispatchThread) .java:91)