java读写文件

import java.io.*;

public class Demo {
    public static void main(String[] args) {
        try {
            // 防止文件建立或读取失败，用catch捕捉错误并打印，也可以throw
            String pathname = "F:/input.txt";
            InputStreamReader reader = new InputStreamReader(new FileInputStream(new File(pathname))); // 建立一个输入流对象reader
            BufferedReader br = new BufferedReader(reader); // 建立一个对象，它把文件内容转成计算机能读懂的语言
            /* 写入Txt文件 */
            File writename = new File("F:/output.txt");
            if (writename.exists()) {
                writename.delete();
            }
            writename.createNewFile(); // 创建新文件
            BufferedWriter out = new BufferedWriter(new FileWriter(writename));
            String line = null;
            while ((line = br.readLine()) != null) {
                out.write(line + "\r\n"); // \r\n即为换行
            }
            out.flush(); // 把缓存区内容压入文件
            out.close(); // 最后记得关闭文件
            br.close();
            reader.close();

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

//同过判断文件的结尾来读取文件   
import java.io.File;   
import java.io.InputStream;   
import java.io.FileInputStream;   
public class InputStreamDemo02   
{   
    public static void main(String args[]) throws Exception{   
        File f = new File("E:"+File.separator+"java2"+File.separator+"StreamDemo"+File.separator+"test.txt");   
        InputStream in = new FileInputStream(f);   
        byte b[] = new byte[1024];   
        int len = 0;   
        int temp=0;          //所有读取的内容都使用temp接收   
        while((temp=in.read())!=-1){    //当没有读取完时，继续读取   
            b[len]=(byte)temp;   
            len++;   
        }   
        in.close();   
        System.out.println(new String(b,0,len));   
    }   
}