having trouble with java.lang.NullPointerException error, please help me - oop

Question

enter code hereI have a private boolean exist=false;, this is a local variable of my payrool class
I also have a method searchRecord(int payrollPeriod, int empNo)
public void searchRecord(int payrollPeriod, int empNo)
{
for(int x=0;x<100;x++)
{
if(trans[x].getPayrollPeriod() == payrollPeriod && trans[x].getEmpNo() == empNo)
{
payrollCounter=x;
exist=true;
break;
}
}
}
My array trans[] is a Transaction type (I used composition) consist of record which has payrollPeriod and empNo.
My program runs fine whenever files exist, but when the search is resulted to false java.lang.NullPointerException happens...
please help me, what should I do
ERROR:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at payroll.Payroll.searchRecord(Payroll.java:350)
at payroll.Payroll.actionPerformed(Payroll.java:184)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
TRANSACTION CLASS:
package payroll;
public class Transaction extends Employee
{
//local variable
private int payrollPeriod;
private double hoursWorked;
//constructor
public Transaction(int payrollPeriod, int empNo, String name, String department, double payRate, double hoursWorked)
{
super(empNo, name, department, payRate);
this.payrollPeriod=payrollPeriod;
this.hoursWorked=hoursWorked;
}
//methods
public int getPayrollPeriod()
{
return payrollPeriod;
}
public double getHoursWorked()
{
return hoursWorked;
}
}

Answer 1

The array trans[x] contains null values.
You should either:
Not allow null values in the array when building it.
Check for null values in the loop and skip/handle them.
public void searchRecord(int payrollPeriod, int empNo) {
for(int x = 0; x < trans.length; x++) {
if (trans[x] == null) {
System.out.println("Skipped null value in trans[x]");
continue;
}
if (trans[x].getPayrollPeriod() == payrollPeriod && trans[x].getEmpNo() == empNo) {
payrollCounter = x;
exist = true;
break;
}
}
}