[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 + "
";
            }
            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 = 1;
            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");
    }
}