I/O流操作记录

（1）

int len = 0;

byte[] byte_value;

while((len = InputStream.read(byte_value))!=-1){

//这里处理字节

}

当len=-1说明已经读完

（2）

//若文件存在删除，

if (outputImage.exists()) {
    outputImage.delete();
}

//之后创建
outputImage.createNewFile();

//下面是字符串输入输出：

BufferedReader sign_in_reader = new BufferedReader(new InputStreamReader(sign_in_connection.getInputStream()));
while((sign_in_line = sign_in_reader.readLine())!=null){
    sign_in_builder.append(sign_in_line);
}

BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(pic_connection.getOutputStream()));
String pic_json = "{\"pic_id\":\""+sign_in_UserNameET.getText().toString()+"\"}";
writer.write(pic_json,0,pic_json.length());

//创建文件夹

file.mkdirs();

文件存在则删除

if(file.exists()){
file.delete();
}

创建新的文件
file.createNewFile();