在底部，我有一个通用的解决方案来替换文件中的行。但是首先，这是眼前特定问题的答案。辅助功能：
public static void replaceSelected(String replaceWith, String type) { try { // input the file content to the StringBuffer "input" BufferedReader file = new BufferedReader(new FileReader("notes.txt")); StringBuffer inputBuffer = new StringBuffer(); String line; while ((line = file.readLine()) != null) { inputBuffer.append(line); inputBuffer.append('n'); } file.close(); String inputStr = inputBuffer.toString(); System.out.println(inputStr); // display the original file for debugging // logic to replace lines in the string (could use regex here to be generic) if (type.equals("0")) { inputStr = inputStr.replace(replaceWith + "1", replaceWith + "0"); } else if (type.equals("1")) { inputStr = inputStr.replace(replaceWith + "0", replaceWith + "1"); } // display the new file for debugging System.out.println("----------------------------------n" + inputStr); // write the new string with the replaced line OVER the same file FileOutputStream fileOut = new FileOutputStream("notes.txt"); fileOut.write(inputStr.getBytes()); fileOut.close(); } catch (Exception e) { System.out.println("Problem reading file."); }}然后调用它：
public static void main(String[] args) { replaceSelected("Do the dishes", "1"); }原始文本文件内容：
Do the dishes0Feed the dog0Cleaned my room1
Output:
Do the dishes0Feed the dog0Cleaned my room1
Do the dishes1Feed the dog0Cleaned my room1
New text file content:
Do the dishes1Feed the dog0Cleaned my room1
And as a note, if the text file was:
Do the dishes1Feed the dog0
Cleaned my room1并且你使用了方法replaceSelected(“Do the dishes”, “1”);，它将不会更改文件。
由于这个问题非常具体，因此我将在此处为将来的读者添加一个更通用的解决方案（基于标题）。
// read file one line at a time// replace line as you read the file and store updated lines in StringBuffer// overwrite the file with the new linespublic static void replaceLines() { try { // input the (modified) file content to the StringBuffer "input" BufferedReader file = new BufferedReader(new FileReader("notes.txt")); StringBuffer inputBuffer = new StringBuffer(); String line; while ((line = file.readLine()) != null) { line = ... // replace the line here inputBuffer.append(line); inputBuffer.append('n'); } file.close(); // write the new string with the replaced line OVER the same file FileOutputStream fileOut = new FileOutputStream("notes.txt"); fileOut.write(inputBuffer.toString().getBytes()); fileOut.close(); } catch (Exception e) { System.out.println("Problem reading file."); }}
