在存儲用戶輸入前檢查退出程序

Question

我有一個幾乎完成的程序。唯一的問題是當用戶輸入「exit」殺死程序時，「exit」這個詞被寫入文件「quotes.txt」中。如何讓程序先檢查「退出」，而不是寫入「quotes.txt」？

下面是代碼：

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

    final Formatter fo; 
    BufferedWriter bw = null; 
    BufferedReader in = new BufferedReader(new FileReader("quotes.txt")); 
    String input = ""; 
    String line; 

    File quotesFile = new File("quotes.txt"); 

    if (quotesFile.exists()) { 
     System.out.println(quotesFile.getName() + " exists."); 
    } else { 
     System.out.println("THIS DOES NOT EXIST."); 
    } 

    try { 
     fo = new Formatter("quotes.txt"); 
     System.out.println("File created or found."); 

    } catch (Exception e) { 
     System.out.println("You have an error."); 
    } 

    do { 
     try { 
      Scanner kb = new Scanner(System.in); 

      if (!input.equalsIgnoreCase("exit")) { 

       System.out.println("Enter your text(Type 'exit' to close program.): "); 
       bw = new BufferedWriter(new FileWriter(quotesFile, true)); 
       input = kb.nextLine(); 
       bw.write(input); 
       bw.newLine(); 
       bw.close(); 
       System.out.println("Entry added.\n"); 
      } 

     } catch (Exception e) { 
      System.out.println("Error."); 
     } 
    } while (!input.equalsIgnoreCase("exit")); 

    System.out.println("Results: "); 

    while ((line = in.readLine()) != null) { 
     System.out.println(line); 
    } 

} 
} 

Answer 1

檢查輸入是其寫入文件之前什麼。

  System.out.println("Enter your text(Type 'exit' to close program.): "); 
      bw = new BufferedWriter(new FileWriter(quotesFile, true)); 
      input = kb.nextLine(); 
      if(!input.equalsIgnoreCase("exit")) { 
       bw.write(input); 
       bw.newLine(); 
       bw.close(); 
       System.out.println("Entry added.\n"); 
      } 
     } 

Answer 2

您只能實現一次掃描儀和書寫器的實例。問題的關鍵在於您在測試後檢查輸入。請注意，您重複測試：if中的一個，while中的另一個。我建議你這個算法：

Scanner kb = new Scanner(System.in); 
input = kb.nextLine(); 

while (!input.equalsIgnoreCase("exit")) { 
    try { 
     System.out.println("Enter your text(Type 'exit' to close program.): "); 
     bw = new BufferedWriter(new FileWriter(quotesFile, true)); 
     bw.write(input); 
     bw.newLine(); 
     bw.close(); 
     System.out.println("Entry added.\n"); 
    } catch (Exception e) { 
     System.out.println("Error."); 
    } 
    input = kb.nextLine(); 
} 

請注意，do...while不能最好地響應您的需求。