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My firebase database looks likes this

The blue rectangle is the data I want to retrieve.

Modal class for the blue rectangle looks like this

public class TripToCompany implements Serializable 

String tripDate;
String companyName;
String vehicleNo;
boolean isFinished;
String firstPickUp;
String inTime;
ArrayList<EmpToCompany> emptoCompanyList;

public TripToCompany() 


public TripToCompany(String tripDate, String companyName, String vehicleNo, boolean isFinished, String firstPickUp, String inTime, ArrayList<EmpToCompany> emptoCompanyList) 
 this.tripDate = tripDate;
 this.companyName = companyName;
 this.vehicleNo = vehicleNo;
 this.isFinished = isFinished;
 this.firstPickUp = firstPickUp;
 this.inTime = inTime;
 this.emptoCompanyList = emptoCompanyList;


public TripToCompany(String tripDate, String companyName, String vehicleNo) 
 this.tripDate = tripDate;
 this.companyName = companyName;
 this.vehicleNo = vehicleNo;
 this.isFinished = false;
 this.inTime = "-";
 this.emptoCompanyList = new ArrayList<>();


public String getTripDate() 
 return tripDate;


public void setTripDate(String tripDate) 
 this.tripDate = tripDate;


public String getCompany() 
 return companyName;


public void setCompany(String companyName) 
 this.companyName = companyName;


public String getVehicleNo() 
 return vehicleNo;


public void setVehicleNo(String vehicleNo) 
 this.vehicleNo = vehicleNo;


public boolean isFinished() 
 return isFinished;


public void setFinished(boolean isFinished) 
 this.isFinished = isFinished;


public String getFirstPickUp() 
 return firstPickUp;


public void setFirstPickUp(String firstPickUp) 
 this.firstPickUp = firstPickUp;


public String getInTime() 
 return inTime;


public void setInTime(String inTime) 
 this.inTime = inTime;


public ArrayList<EmpToCompany> getEmptoCompanyList() 
 return emptoCompanyList;


public void setEmptoCompanyList(ArrayList<EmpToCompany> emptoCompanyList) 
 emptoCompanyList = emptoCompanyList;


public void addEmpToCompanyList(EmpToCompany etc) 
 if (emptoCompanyList.size() == 0) 
 firstPickUp = etc.getCabInTime();
 
 emptoCompanyList.add(etc);

 

I am fetching the data from firebase using the standard query. Here is the code

 FirebaseDatabase defaultDatabase = FirebaseDatabase.getInstance();
 DatabaseReference mRef = defaultDatabase.getReference("data");
 Query query = mRef.child("toComp/" + companyId + "/" + fromDate + "/" + shiftTimeId + "/");
 query.addListenerForSingleValueEvent(new ValueEventListener() 
 @Override
 public void onDataChange(DataSnapshot ds) 

 if (ds.exists()) 
 System.out.println("exist");
 for (DataSnapshot singleSnapshot : ds.getChildren()) 
 TripToCompany trpObj = (TripToCompany) singleSnapshot.getValue(TripToCompany.class);
 ArrayList<EmpToCompany>ee= trpObj.getEmptoCompanyList();
 System.out.println("Company Name: "+trpObj.getCompany()); //successfully retrived
 System.out.println("Employee Count: " + ee.size()); //unable to fetch it. Gives NullPointerException

 
 else 
 System.out.println("error");
 
 

 @Override
 public void onCancelled(DatabaseError de) 
 );

I am able to get the remaining data successfully from firebase. The data in red rectangle is the ArrayList, and I am unable to fetch it(show in red rectangle in the image). I have printed in the console using Sysout and I am unable to get ArrayList data. It returns NullPointerException. How can I fetch that ArrayList in the TripToCompany Object?

To solve this, please change the following lines of code:

public void setEmptoCompanyList(ArrayList<EmpToCompany> emptoCompanyList) 
 emptoCompanyList = emptoCompanyList;

to

public void setEmptoCompanyList(ArrayList<EmpToCompany> emptoCompanyList) 
 this.emptoCompanyList = emptoCompanyList;
// ^

You should assign the value of the local emptoCompanyList variable to the member class (this) field, not to the same variable.