java - 文件输入/输出

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关闭。此题需要 details or clarity 。目前不接受答案。

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有人要求我将当前的程序保存到一个文件中，以便以后即使程序结束也可以继续。不过我是java新手，所以如果有人可以帮助我，我将非常感激:)这是我设法完成的代码，但它只是创建一个空文件，我该如何解决这个问题？

下面不是整个程序编码，我只是复制了相关的代码。

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.FileWriter;


public static void main (String[] param) throws FileNotFoundException
{
 try 
    {
    fileinputoutput ();
    } 
    catch (FileNotFoundException e) 
    {
   System.exit(0);
    }
} // END main



public static void fileinputoutput() throws FileNotFoundException
 {

    File input = new File("input.txt");
    File output = new File("loveletter.txt");
    PrintWriter outputFile = new PrintWriter(output);

    Scanner check = new Scanner(System.in);

    String filename = check.nextLine();
    File inputfile = new File(filename);

    Scanner newfile = new Scanner(inputfile);
    newfile.close();

    while(newfile.hasNext())
    {

    String write = newfile.nextLine();
    System.out.println(write);

    }

    outputFile.close();

}

Answer 1

答案很明显。您只得到一个空白文件的原因是您从未通过 outputFile 写入任何内容，并在对其执行任何操作之前关闭 newfile。你应该尝试这样的事情:

public static void fileinputoutput() throws FileNotFoundException {
    File input = new File("input.txt"); // What do you use this variable for? It's never used in the code fragment you posted
    File output = new File("loveletter.txt");
    PrintWriter outputFile = new FileWriter(output); // I'd personally use FileWriter here
    Scanner check = new Scanner(System.in);
    String filename = check.nextLine();
    File inputFile = new File(filename);
    Scanner newfile = new Scanner(inputFile);

    while(newfile.hasNext()) {
        String write = newfile.nextLine();
        outputFile.println(write); // You used to only output something to the console here
    }

    outputFile.close();
    newfile.close();
    check.close();
}