I get null pointer exception

Question

I have three class as boat,car,truck etc who extend from vehicle , I write all the object of this in a file say vehicleOrder.dat like this :

fout = new FileOutputStream("VehicleOrders.dat");   
oos = new ObjectOutputStream(fout); 
oos.writeObject(v); //where v is object of boat,truck car etc

Till here its good ,it writes, but when I try to read the dat file like this,

fin = new FileInputStream("VehicleOrders.dat");
ois = new ObjectInputStream(fin);
vehicle readInstance=null;

do{
    readInstance = (vehicle)ois.readObject();
    if(readInstance != null)
    {
        orderList.add(readInstance);
    } 
}       
while (readInstance != null);

it reads the two objects which are in the dat file but after that goes to the do again and gives null pointer exception

See this question http://stackoverflow.com/questions/18689814/invalid-class-exception-no-valid-constructor — Cyrille Ka, Oct 10 '13 at 01:21

score 1 · Answer 1 · edited May 23 '17 at 12:05

1

It seems like your class doesn't have 0-param-Constructor. Maybe this link will help you out about the explanation

edited May 23 '17 at 12:05

Community

1
1

answered Oct 10 '13 at 01:22

Agung Pratama

3,666
7
36
77

score 0 · Answer 2 · answered Oct 10 '13 at 01:22

0

ObjectInputStream expects a visible no-arg constructor for the class instance you are trying to deserialize. I assume your class doesn't have one. Add one.

answered Oct 10 '13 at 01:22

Sotirios Delimanolis

274,122
60
696
724

Yeah I search the net and found the same solution , now that excpetion is through but now I get Null pointer exception in the same line :( – Snedden27 Oct 10 '13 at 01:27
@Snedden27 Which line is that? Please post a full stack trace by editing your question. – Sotirios Delimanolis Oct 10 '13 at 01:30
1

@Snedden27 You can edit your own question. Whatever post it here or just tell us exactly what the error is. – Sotirios Delimanolis Oct 10 '13 at 01:38

I get null pointer exception

2 Answers2