java 对比两文件哪行被更改了

package iO;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Date;

public class Exr {
        public void Compare(File file1,File file2){

        try {
Date l1= new Date(file1.lastModified());
Date l2= new Date(file2.lastModified());
       System. out .println(l1+"  " +l2);

              FileReader fr1= new FileReader(file1);
              
              FileReader fr2= new FileReader(file2);
               BufferedReader br2= new BufferedReader (fr2);

               BufferedReader br1= new BufferedReader (fr1);
              String s1= null ;
String s= null;
               while ((s=br1.readLine())!= null){
                     s1=br2.readLine();
                      if (s.equals(s1)){
                     System. out .print(s+"\t" );
                     System. out .println(s1);}
                      else {
                           System. out .print(s+"\t" );
                   System. out .println(s1+"<--此行被更改了" );         }
              }
       } catch (FileNotFoundException e) {
               // TODO 自动生成的 catch 块
              e.printStackTrace();
       } catch (IOException e) {
               // TODO 自动生成的 catch 块
              e.printStackTrace();
       }
       }

        public static void main(String[] args) {
Exr ex= new Exr();
ex.Compare( new File( "d:\\123.txt" ), new File("d:\\1222.txt" ));
       }
       

}