文件读写

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读文件：先得到文件地址如："E:\\old.txt",这里绝对路径时有'\',要用双的；

然后得到文件句柄：File file = new File("filePath");

判断文件是否存在 if(file.isFile() && file.exists());

获得一个输入流，可以读文件：InputStreamReader read = new InputStreamReader(new FileInputStream(file), encoding);

//endcoding 是一个String类型字符串，编码格式

获得一个读入缓冲BufferedReader br = new BufferedReader(read);

然后开始读。

写文件：

获得文件句柄:File file = new File("E:\\new.txt");

得到输出流：OutputStream os = new FileOutputStream(file);

得到一个打印流:PrintStream ps = new PrintStream(os);

写：ps.print(String s);

注意：写文件时，经常不能写出换行

因为写在s后加换行是s.append("\r\n");

源码：

public class CMain {

   public static void main(String[] args) {
       String filePath = "E:\\old.txt";

       StringBuffer buffer = new StringBuffer("Only a test\n");
       File file = new File("E:\\new.txt");
       try {
           OutputStream os = new FileOutputStream(file);
           readTxtFile(filePath, os);
       } catch (FileNotFoundException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
       System.out.println("over!!!!!!");
   }
//读文件
   public static void readTxtFile(String filePath, OutputStream os) {
       try {
           String encoding = "GBK";
           File file = new File(filePath);
           if (file.isFile() && file.exists()) {
               InputStreamReader read = new InputStreamReader(
                       new FileInputStream(file), encoding);
               BufferedReader bufferedReader = new BufferedReader(read);
               String lineTxt = null;
               while ((lineTxt = bufferedReader.readLine()) != null) {
                   StringBuffer sb = new StringBuffer(lineTxt);
                   sb.append("\r\n");
                   writeFromBuffer(sb, os);
//                   writeFromBuffer("\r\n", os);
               }
               read.close();
           } else {
               System.out.println("找不到指定文件");
           }
       } catch (Exception e) {
           System.out.println("读取文件内容出错");
           e.printStackTrace();
       }
   }
//写入
   public static void writeFromBuffer(StringBuffer buffer, OutputStream os) {
       PrintStream ps = new PrintStream(os);
       ps.print(buffer.toString());
   }

   public static void writeFromBuffer(String string, OutputStream os) {
       StringBuffer sb = new StringBuffer(string);
       writeFromBuffer(sb, os);
   }
}

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