java - 将行写入输出文件(java)后尝试打印它们

Question

我有一个问题。我基本上被要求使用一种方法从输出文件进行打印。因此，首先，我实际上开始用行填充输出文件......然后，当我尝试实际读取它们并将它们打印在屏幕上时，出现了一个小问题。我实际上使用了“调试”选项，问题出在“line = input.nextLine()”代码行内，但我真的不知道为什么......我的意思是这就是我们从输出中读取的方式文件...帮助将不胜感激。

这是我迄今为止的工作:

import java.util.*;
import java.io.*;

public class Problem_3 {

    public static void main(String[] args) {

        PrintWriter outFile = null;
        File f1 = new File("try.txt");


        try {

            outFile = new PrintWriter("try.txt");
            outFile.println("First line!");
            outFile.println("Second line!");
            outFile.println("Third line!");

            cat(f1);
        } catch (Exception e) {
            outFile.print("(1) Exception: " + e.getMessage()); // no such element exception
        }

        outFile.close();
    }
    /*
     * outFile = new PrintWriter(f1); outFile.println("Line 1");
     * outFile.println("Line 2"); outFile.println("Line 3"); outFile.print("");
     * cat(f1); } catch (Exception e) { System.out.println("(1)Exception: " +
     * e.getMessage()); } outFile.close(); }
     */

    public static void cat(File file) throws FileNotFoundException {

        Scanner input = null;
        String line = "";

        input = new Scanner(new FileReader(file));
        //line = input.next();
        //  line = input.nextLine();// this line calls the exception in the main method

        while ((line != null)) {
            System.out.println("In the while loop");
            System.out.println("Line  323" + line);
            return;
        }
        input.close();
    }
}

Answer 1

修改代码为:

try {

    outFile = new PrintWriter("try.txt");
    outFile.println("First line!");
    outFile.println("Second line!");
    outFile.println("Third line!");

    outFile.close();


 } 
 catch (Exception e) {
    outFile.print("(1) Exception: " + e.getMessage()); // no such element exception
 }

 cat(f1);

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