文件I / O錯誤

Question

我剛剛開始使用Murach的Se 6中的示例進行文件I / O andim。這是我的代碼。 我錯過了什么嗎？ 我知道進一步的代碼還有更多，但由於這是一個示例，因此應該正確嗎？

//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();


    }

}

//回答

通過在我初始化主要代碼的末尾添加throws異常，此代碼有效。 甚至txt文件products.txt都位於預期的class文件夾中。 //導入import java.io. *; 與文件I / O方法一起使用。

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

問題是對java.io包的許多調用都引發異常。

輕松解決：將以下內容添加到您的方法簽名中

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

幾乎一樣容易解決：添加try / catch / finally塊。

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();
    }

}

編輯：您知道您試圖兩次調用out.close()嗎？ 第二個應該是對in.close()的調用