用一个文件名替换另一个文件名 扩展名不变 修改后的文件另存

import java.io.*;
public class Test{
 public static void main(String[] args)
 {
  if(args.length<3)
  {
   System.out.println(args.length);
    return;
  }
  
  else{
   java.io.File f1=new File(args[0]);
   java.io.File f2=new File(args[1]);
   java.io.File path=new File(args[2]);
   String newname;
   if(f1.isFile()&&f2.isFile()&&path.isDirectory())
   {
    try{
    
     String fn1=f1.getName();
     fn1=fn1.substring(0,fn1.lastIndexOf("."));
     String fn=f2.getName();
     newname=fn1+fn.substring(fn.lastIndexOf("."),fn.length());
     newname=path.getCanonicalPath()+newname;
     
     File f3=new File(newname);
     
     if(!f3.exists())
      f3.createNewFile();
     java.io.DataInputStream ids=new java.io.DataInputStream(new FileInputStream(f2));
     java.io.DataOutputStream ods=new java.io.DataOutputStream(new FileOutputStream(f3));
     byte[] bt=new byte[4096];
     while(ids.available()>0){
      
      ids.read(bt);
      
      ods.write(bt);
     } 
     ids.close();
     ods.close();
    }catch(Exception e){
     e.printStackTrace();
     return;
    }
    System.out.println("file "+f2.getAbsolutePath()+" successfully copied to "+newname);
   
   }
   
   
   
  }
 }
}