我的Java Palindrome程序中的簡單錯誤（循環時）幫助

Question

我正在用Java構建回文程序。 任務是從文件中讀取單詞，確定文件中的單詞是否是回文，然后將結果發送到另一個文件。 我可以正常工作，但是程序中唯一的問題是它只會讀取第一個單詞。 我需要它來讀取文件中的所有行。 我的代碼是：

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

public class str1 {

    public static void main(String args[]) {
      try {

      String reverse = "";
      System.out.print("Enter the name of the input file: ");
      Scanner keyboard = new Scanner(System.in);
      String a = keyboard.nextLine();
      int length = a.length();
      File inFile = new File(a);
      Scanner fin = new Scanner(inFile);
      System.out.print("Enter name of the output file: ");
      String outFileName= keyboard.nextLine();
      File outFile = new File(outFileName);
      PrintWriter fout = new PrintWriter(outFile);
      while ( fin.hasNext(a) ) {
      for ( int i = length - 1; i >= 0; i-- )
     reverse = reverse + a.charAt(i);

  if (a.equals(reverse))
     fout.println("Entered string is a palindrome.");
  else
     fout.println("Entered string is not a palindrome.");
      }
      fin.close();
      fout.close();
      System.out.print("Done. See '" + outFileName + "'.");
      } catch (Exception e) {
          e.printStackTrace();
      }
    }
}

我試圖將第23行中的while更改為“ while（fin.hasNextLine（a））{”，但沒有成功。 我相信這就是為什么它不會閱讀第一行的原因。 任何幫助是極大的贊賞。

Answer 1

這應該工作。 您需要在檢查輸入文件的while條件之后添加nextLine方法，以進行實際處理，並且還需要在讀取單詞后檢查單詞的長度：

導入java.io.File; 導入java.io.PrintWriter; 導入java.util.Scanner;

public class Str1 {

    public static void main(String args[]) {

        try {

            String reverse = "";
            System.out.print("Enter the name of the input file: ");
            Scanner keyboard = new Scanner(System.in);
            String a = keyboard.nextLine();
            File inFile = new File(a);
            Scanner fin = new Scanner(inFile);
            System.out.print("Enter name of the output file: ");
            String outFileName = keyboard.nextLine();
            File outFile = new File(outFileName);
            PrintWriter fout = new PrintWriter(outFile);
            while (fin.hasNext()) {
                String temp = fin.nextLine();
                int length = temp.length();
                for (int i = length - 1; i >= 0; i--)
                    reverse = reverse + a.charAt(i);

                if (a.equals(reverse))
                    fout.println("Entered string is a palindrome.");
                else
                    fout.println("Entered string is not a palindrome.");
            }
            keyboard.close();
            fin.close();
            fout.close();
            System.out.print("Done. See '" + outFileName + "'.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Answer 2

@QQ_At_The_PewPew，您犯了一個錯誤，正在對字符串“ a”應用反向，這是您的文件名，而不是文件輸入。

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

public class str1 {

    public static void main(String args[]) {
      try {

      String reverse = "";
      System.out.print("Enter the name of the input file: ");
      Scanner keyboard = new Scanner(System.in);
      String a = keyboard.nextLine();
      int length = a.length();
      File inFile = new File(a);
      Scanner fin = new Scanner(inFile);
      System.out.print("Enter name of the output file: ");
      String outFileName= keyboard.nextLine();
      File outFile = new File(outFileName);
      PrintWriter fout = new PrintWriter(outFile);
      while ( fin.hasNext() ) {
      String s=fin.nextLine();
      for ( int i = length - 1; i >= 0; i-- )
     reverse = reverse + s.charAt(i);

  if (s.equals(reverse))
     fout.println("Entered string is a palindrome.");
  else
     fout.println("Entered string is not a palindrome.");
      }
      fin.close();
      fout.close();
      System.out.print("Done. See '" + outFileName + "'.");
      } catch (Exception e) {
          e.printStackTrace();
      }
    }
}