[Java文件操作] 为文本文件添加行号

【思路】将文件中的内容按行读取存入一个字符串中，在输出时再为每一行加上行号。

 import java.io.*;
 public class Text {
     private String strFinal = "";
     public void open(String fileName) {
         try {
             BufferedReader in = new BufferedReader(new FileReader(fileName));
             String s = null;
             while ((s = in.readLine()) != null) {
                 strFinal = strFinal + s + "\n";
             }
             in.close();
         } catch (IOException e) {
             System.out.println(e);
         }
     }
     public void save(String fileName){
         try{
             BufferedReader in = new BufferedReader(new StringReader(strFinal));
             PrintWriter out = new PrintWriter(new FileWriter(fileName));
             int lineCount = ;
             String s = null;
             while((s = in.readLine())!=null){
                 out.println(lineCount+++": "+s);
             }
             in.close();
             out.close();
         }catch(IOException e){
             System.out.print(e);
         }
     }
     public static void main(String args[])throws IOException{
         Text obj = new Text();
         obj.open("D:/Java_workspace/Text/src/Text.java");
         obj.save("E:\\Example\\A.txt");
     }
 }