Eclipse java字符大小写

每个字符应在大写和小写之间切换。我的问题是我不能让它正常工作。这就是我到目前为止所做的：

        oneLine = br.readLine();
        while (oneLine != null){  // Until the line is not empty (will be when you reach End of file)
            System.out.println (oneLine);    // Print it in screen
            bw.write(oneLine); // Write the line in the output file 
            oneLine = br.readLine(); // read the next line
        }
        int ch;
        while ((ch = br.read()) != -1){

            if (Character.isUpperCase(ch)){
                Character.toLowerCase(ch);

            }
            bw.write(ch);


        }

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给你。您遇到了一些问题：

您从未实际存储字符大小写切换的结果

您需要将换行符与每行一起保存

为了便于阅读，我打开了箱子开关

以下是修改后的代码：

  public static void main(String args[]) {
    String inputfileName = "input.txt"; // A file with some text in it
    String outputfileName = "output.txt"; // File created by this program
    String oneLine;

    try {
      // Open the input file
      FileReader fr = new FileReader(inputfileName);
      BufferedReader br = new BufferedReader(fr);

      // Create the output file
      FileWriter fw = new FileWriter(outputfileName);
      BufferedWriter bw = new BufferedWriter(fw);

      // Read the first line
      oneLine = br.readLine();
      while (oneLine != null) { // Until the line is not empty (will be when you reach End of file)
        String switched = switchCase(oneLine); //switch case
        System.out.println(oneLine + " > "+switched); // Print it in screen
        bw.write(switched+"\n"); // Write the line in the output file
        oneLine = br.readLine(); // read the next line
      }

      // Close the streams
      br.close();
      bw.close();
    } catch (Exception e) {
      System.err.println("Error: " + e.getMessage());
    }
  }

  public static String switchCase(String string) {
    String r = "";
    for (char c : string.toCharArray()) {
      if (Character.isUpperCase(c)) {
        r += Character.toLowerCase(c);
      } else {
        r += Character.toUpperCase(c);
      }
    }
    return r;
  }

---

这段代码是否有效（即编译和运行时没有运行时错误）？它有什么作用？你认为它为什么这样做？

$tr'A-Za-z'A-Za-z'output.txt