Common problems in io streams

1.IO
1.1 summary
Flow is a set of sequential , Set of bytes with start and end points , Is the general term or abstraction of data transmission . That is, the transmission of data between two devices is called streaming , The essence of stream is data transmission , According to the characteristics of data transmission, streams are abstracted into various kinds , Convenient and more intuitive data operation .
I：input Input stream
O：output： Output stream
1.2 classification
According to the type of data processed , It is divided into byte stream and character stream
It is divided into input flow and output flow according to different data flow directions .（ In and out are relative to memory ）

According to different functions , It is divided into node flow and processing flow
Node flow ： Direct manipulation of data sources
Processing flow ： Process other streams
1.3 Four abstract classes

 1.3.1  InputStream

 1.3.2 OutPutStream

 1.3.3  Reader

 1.3.4  Writer

 

1.4 File stream
1.4.1 FileInputStream
summary ： Used to open the file and read the data in the file
Want to read a file , You must find it first , You must use this file stream
1. Absolute position
The system root directory shall prevail , such as D：/xxx/xxx/xxx/a.txt
2. The relative position
./ Represents the current directory
…/ Indicates the parent directory
…/…/ Go to the superior directory

Common methods

1.4.2 Read Use
read： Read a byte , And return the corresponding ASCLL Code value , Return to int type , If you reach the end of the file （ After reading the ） Then return to -1
read Method overloading ： You can pass an array , One read will fill the array / After reading , And then back in one go
return int type , Is the current number of reads , If the end of the file is reached return -1
The array is equivalent to a buffer , It will improve efficiency

 

1.4.3 FileReader
summary ： FileReader： Read one character at a time , That's two bytes , Mainly used to read plain text , Solve the mess
read（）： Read one character at a time , Return the corresponding ASCLL code , Return at the end -1
read（char[]）: Read one character array at a time , Improve reading efficiency , Returns the number of characters read locally , Return at the end of the file -1
Usage mode

 

 1.5 Buffer flow

  characteristic

1. It exists mainly to improve efficiency , Reduce the number of physical reads
2. Provide readLine()、newLine() Such a convenient way （ For buffered character stream ）
3. When reading and writing , There will be a cache part , call flush To refresh the cache , Write memory data to disk

5.1 BufferedReader

1.5.2 BufferedWriter

 

 

1.6  Converted flow

 

 1.7  Print stream

 

 1.8    Data flow