Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException For Loops -

i have problem loop because of nullpointerexception error.

for (int num = 0; num < checkingacct.getsize(); num++) 

and error comes as:

exception in thread "awt-eventqueue-0" java.lang.nullpointerexception @ application2.panel.listtransactions(panel.java:152) @ application2.application2$application2a.actionperformed(application2.java:84) @ javax.swing.abstractbutton.fireactionperformed(abstractbutton.java:2018) @ javax.swing.abstractbutton$handler.actionperformed(abstractbutton.java:2341) @ javax.swing.defaultbuttonmodel.fireactionperformed(defaultbuttonmodel.java:402) @ javax.swing.jtogglebutton$togglebuttonmodel.setpressed(jtogglebutton.java:308) @ javax.swing.plaf.basic.basicbuttonlistener.mousereleased(basicbuttonlistener.java:252) @ java.awt.component.processmouseevent(component.java:6505) @ javax.swing.jcomponent.processmouseevent(jcomponent.java:3320) @ java.awt.component.processevent(component.java:6270) @ java.awt.container.processevent(container.java:2229) @ java.awt.component.dispatcheventimpl(component.java:4861) @ java.awt.container.dispatcheventimpl(container.java:2287) @ java.awt.component.dispatchevent(component.java:4687) @ java.awt.lightweightdispatcher.retargetmouseevent(container.java:4832) @ java.awt.lightweightdispatcher.processmouseevent(container.java:4492) @ java.awt.lightweightdispatcher.dispatchevent(container.java:4422) @ java.awt.container.dispatcheventimpl(container.java:2273) @ java.awt.window.dispatcheventimpl(window.java:2719) @ java.awt.component.dispatchevent(component.java:4687) @ java.awt.eventqueue.dispatcheventimpl(eventqueue.java:735) @ java.awt.eventqueue.access$200(eventqueue.java:103) @ java.awt.eventqueue$3.run(eventqueue.java:694) @ java.awt.eventqueue$3.run(eventqueue.java:692) @ java.security.accesscontroller.doprivileged(native method) @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:76) @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:87) @ java.awt.eventqueue$4.run(eventqueue.java:708) @ java.awt.eventqueue$4.run(eventqueue.java:706) @ java.security.accesscontroller.doprivileged(native method) @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:76) @ java.awt.eventqueue.dispatchevent(eventqueue.java:705) @ java.awt.eventdispatchthread.pumponeeventforfilters(eventdispatchthread.java:242) @ java.awt.eventdispatchthread.pumpeventsforfilter(eventdispatchthread.java:161) @ java.awt.eventdispatchthread.pumpeventsforhierarchy(eventdispatchthread.java:150) @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:146) @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:138) @ java.awt.eventdispatchthread.run(eventdispatchthread.java:91) 

the loop line 152. application2 line 84

 if (codee == dos)            panel.listtransactions(); <-----  

and getsize:

public int getsize(){     transsize = translist.size();     return transsize; } 

based on google findings, nullpointerexception means didn't initialize something. don't know intialize. transsize initialized 0.

thank you~

based on error happening @ loop, suspect checkingacct null. make sure using constructor initialize:

checkingaccount checkingacct = new checkingaccount();.

if you're doing that, make sure it's not being assigned null anywhere else in code.