Question

I just started doing file I/O andim using an example from Murach’s Se 6.
Here is my code. Am i missing something. I know the code further on has more but as this is an example this should work right?

//Import import java.io.*; for use with the File I/O Methods.
import java.io.*;
public class MainApp 
{

    public static void main(String[] args) 
    {
    //Create a file object.
    File productFile = new File("product.txt");
    //Open a buffered output stream to allow write to file operations.
    PrintWriter out = new PrintWriter(
                      new BufferedWriter(
                      new FileWriter(productFile)));      

    out.println("java\tMurach's Beginning Java 2\t$49.99");
    out.close();

    BufferedReader in = new BufferedReader(
                        new FileReader(productFile));

    String line = in.readLine();
    System.out.println(line);

    out.close();


    }

}

//Answer

by adding a throws exception to the end of where i initialised the main this code works. Even the txt file products.txt is in the class folder as expected.
//Import import java.io.*; for use with the File I/O Methods.

import java.io.*;
public class MainApp 
{

    public static void main(String[] args) throws Exception 
    {
    //Create a file object.
    File productFile = new File("product.txt");
    //Open a buffered output stream to allow write to file operations.
    PrintWriter out = new PrintWriter(
                      new BufferedWriter(
                      new FileWriter(productFile)));      

    out.println("java\tMurach's Beginning Java 2\t$49.99");
    out.close();

    BufferedReader in = new BufferedReader(
                        new FileReader(productFile));

    String line = in.readLine();
    System.out.println(line);

    out.close();


    }

}

Answer 1

The problem is that a number of the calls to the java.io package throw exceptions.

easy fix: add the following to your method signature

 public static void main(String[] args) throws IOException 

almost as easy fix: add try/catch/finally blocks.

public static void main(String[] args) 
{
    //Create a file object.
    File productFile = new File("product.txt");

    //Open a buffered output stream to allow write to file operations.
    PrintWriter out = null;
    try {   
        out = new PrintWriter(
                new BufferedWriter(
                        new FileWriter(productFile)));      

        out.println("java\tMurach's Beginning Java 2\t$49.99");
    }
    catch(IOException ex) {
        // todo exception handling

        System.out.println("ERROR! " + ex);

    }
    finally {
        out.close();

    }

    BufferedReader in = null;
    try {
        in = new BufferedReader(
                new FileReader(productFile));

        String line = in.readLine();
        System.out.println(line);
    }
    catch (IOException ex) {
        // todo more exception handling
        System.out.println("ERROR! " + ex);
    }
    finally {
        in.close();
    }

}

edit: you know you are trying to call out.close() twice? The second should be a call to in.close()