FileReader  fr =new FileReader("b.txt");//绑定源文件

 FileWriter  fw= new FileWriter("a.txt");

 char[]  c= new char[1024];

 int  len=0;

 //循环读取

 while((len=fr.read(c))!=-1){

     fw.write(c,0,len);

 }

 //关流

 fw.close();

 fr.close();