Java文件的读写

//读取文件
FileReader reader=new FileReader("D:\\ss\\1.txt");
//bufferReader效率比较高
BufferedReader bf=new BufferedReader(reader);
String line;
StringBuilder sb=new StringBuilder();
int i=1;
while((line=bf.readLine())!=null){
     sb.append(line);
System.out.println("第"+i+"行："+line);
i++;
}
//写入文件
FileWriter writer=new FileWriter("D:\\ss\\2.txt");
//BufferedWriter bufwriter=new BufferedWriter(writer);
writer.write(sb.toString(),0,sb.length());
writer.flush();

OutputStreamWriter ow=new OutputStreamWriter(new FileOutputStream("D:\\ss\\3.txt"));
ow.write(sb.toString(),0,sb.length());

PrintWriter pw=new PrintWriter(new FileOutputStream("D:\\ss\\4.txt"),true);
pw.write(sb.toString(),0,sb.length());
pw.println(sb.toString());