Question

I’m getting the below exception in my java project.

Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at com.ooad.ooadfirstassignment.Employee.readData(Employee.java:25)
    at com.ooad.ooadfirstassignment.Salaried.readData(Salaried.java:16)
    at com.ooad.ooadfirstassignment.Factory.<init>(Factory.java:21)
    at com.ooad.ooadfirstassignment.MainClass.main(MainClass.java:25)

The Code is as follows :

=====================================================

public class MainClass {

    /**
     * @param args
     */
    public static void main(String[] args) throws IOException
    {
        // TODO Auto-generated method stub
        FileInputStream empTextStreamIn = null;
        try
        {
            empTextStreamIn = new FileInputStream("Employee.txt");
        }
        catch(FileNotFoundException fex)
        {
            System.out.println("Employee File not found");
            fex.printStackTrace();
        }
        Factory f = new Factory(empTextStreamIn);
        empTextStreamIn.close();

    }

}

====================================================================

public class Factory 
{
    public Factory(FileInputStream empTextStreamIn) 
    {
        // TODO Auto-generated constructor stub
        int empType;
        String EmpID = null,DeptID = null;
        double salary=0;
        Scanner sc = new Scanner(empTextStreamIn);
        while(sc.hasNextLine())
        {
            empType = sc.nextInt();
            switch (empType) 
            {
                case 1:Salaried salr = new Salaried(empTextStreamIn);
                        salr.readData();

                                      System.out.println("EmpType="+empType+"   EmpID="+EmpID+"   DeptID="+DeptID+"   Salary="+salary);

The code goes on so this is the main part though.

Next the Employee Class

public class Employee 
{
    String EmpID, DeptID;   //Unique detail for Employee class

    protected Scanner sc;

    Employee()
    {

    }
    public Employee(FileInputStream empTextStreamIn) 
    {
        // TODO Auto-generated constructor stub
        sc = new Scanner(empTextStreamIn);

    }
    void readData()
    {
        String EmpID = sc.next();
        String DeptID = sc.next();
    }

}

Salaried Class

public class Salaried extends Employee
{
    double salary;  //Unique detail for Salaried class

    public Salaried(FileInputStream empTextStreamIn) 
    {
        super(empTextStreamIn);

    }
    void readData()
    {
        super.readData();
        salary = sc.nextDouble();


    }

}

Kindly help me where I’m going wrong.

Answer 1

The problem here is that the Scanner class uses an internal buffer. You create a Scanner object in the Factory class. This Scanner reads from the underlying FileInputStream into its own buffer. I suspect your input file is so small that the whole file fits into this buffer. That means that the Scanner in the Factory will read through the whole FileInputStream. After this, you create a new Scanner object in the Employee class, using the same FileInputStream. However, the first Scanner has already consumed all the content in that FileInputStream. Hence, because there is no data, that Scanner throws an exception.

So what you need is probably just to ensure that you use the same Scanner object when reading from the file, instead of instantiating several different scanners on the same FileInputStream.

<EDIT>

To verify that this is the case, you can try inserting the following line inside the while loop in the Factory class:

System.out.println("Data could be read from the InputFileStream: " 
                    + (empTextStreamIn.read() != -1));

(Note that the read method can throw an IOException, so you will have to surround it with a try-catch block)

</EDIT>