Java 文件IO写入读取四种方法

//先创建一个和硬盘连接的流（打通硬盘和内存的通道）
FileInputStream fis = new FileInputStream("D:\\Demo.txt");
//创建缓存区大小是1k
byte[] bytes = new byte[1024];
int data = 0; //存储有效字节数
StringBuffer sb = new StringBuffer();
//由于文件大小通常远远大于缓冲区大小，所以要循环读取
while((data = fis.read(bytes)) != -1){//返回-1则文件读取完毕，停止循环读取
　　String temp=new String(bytes,0,data);//读取缓冲区的字节数，转换成字符串
　　sb.append(temp);
　　System.out.printlb("====有效字节数===="+data);
}
System.out.printlb(sb.toString());
//关闭流
fis.close();

//创建一个读取文件的流
FileOutputStream fos = new FileOutputStream("E:\\Demo.txt");
String temp = "海内存知己，天涯若比邻。";
//把字符串分解成字节，填到字节数组中
byte[] bytes = temp.getBytes(); 
//写入到指定路径，没有则创建文件
fos.write(bytes);
//关闭流
fos.close();
System.out.println("写入成功！");

Reader fr = new FileReader("E:\\Demo.txt");
char ch[] = new char[1024];
StringBuffer sbf = new StringBuffer();
int length = fr.read(ch);
while (length != -1) {
　　sbf.append(ch);
　　length = fr.read();
}
System.out.println(sbf.toString());
fr.close();

Writer fr = new FileWriter("D:\\Demo.txt");
fr.write("有朋自远方来，不亦乐乎");
fr.close();

Reader fr = new FileReader("D:\\Demo.txt");
BufferedReader br = new BufferedReader(fr);
String line = br.readLine();
while (line != null) {
　　System.out.println(line);
　　line = br.readLine();
}
br.close();
fw.close();

  Writer fw = new FileWriter("D:\\Demo.txt",true);//true 为连续追加
  BufferedWriter bw = new BufferedWriter(fw);
  bw.write("学而时习之，不亦説乎");
  bw.close();
  fw.close();

InputStream is = new FileInputStream("E:\\春暖花开.jpg");
DataInputStream dis = new DataInputStream(is);

OutputStream ops = new FileOutputStream("D:\\春暖花开.jpg");
DataOutputStream dos = new DataOutputStream(ops);

byte[] bytes = new byte[1024];
int date = 0;
while ((date = dis.read(bytes)) != -1) {
dos.write(bytes,0,date);
}

dos.close();
ops.close();
dis.close();
is.close();

System.out.println("复制成功");