Java-->io__java

io

io
Input/output
Input/Output

java.io Bag

File
Randomaccessfile

Inputstream/outputstream the abstract parent class of a byte stream
Fileinputstream/fileoutputstream insert files, read and write directly to file data
Bufferedinputstream/bufferedoutputstream memory buffer to improve single byte read-write efficiency
Datainputstream/dataoutputstream Fixed byte format writeint () writedouble () writeUTF ()
PrintStream any data into a string output print () println ()
Bytearrayinputstream/bytearrayoutputstream with an in-memory byte[] array Tobytearray ()
Objectinputstream/objectoutputstream serialization, deserialization writeobject () ReadObject ()

Abstract parent class for Reader/writer character streams
Inputstreamreader/outputstreamwriter Coded Conversion Stream
Filereader/filewriter is "file byte stream" and "encoded conversion stream"
Bufferedreader/bufferedwriter character Buffering, ReadLine ()
PrintWriter and PrintStream the same File wrapper disk path string

Can encapsulate
*) file path
*) directory path
*) A path that does not exist

Creating objects

1.File f = new File ("D:\abc\a.txt");

2.File f = new File ("D:\abc\", "a.txt");

Method

*) file or directory properties

CanRead () CanWrite () CanExecute () is readable writable 
                executable
        Ishidden ()                  whether                        the path represented by the file exists () is hidden
        GetAbsolutePath ()   full path
        getName ()           file name
        GetParent ()         Parent directory
        lastmodified (  ) The last modification time, the millisecond value
        length ()                file byte amount, invalid directory
        isdirectory ()       whether the folder
        Isfile ()                whether the file
        Gettotalspace () Total space size
        getfreespace ()  free space

*) file or directory operation

        CreateNewFile () Create a file delete
        ()                Delete a file or "Empty directory"
        mkdir ()                 Create a single-tier directory Mkdirs () create a                multi-tier directory
        Renameto ()          renaming, moving

        *) Creating a Delete rename method returns a Boolean indicating whether the operation

        was successful file.createtempfile (prefix,  suffix)        create temporary files in the system temp directory

*) file List

        List ()          returns string[], contains child files, subdirectory name
        listfiles () return file[], file object list containing child files, subdirectories

        (filenamefilter)
        Listfiles (FilenameFilter)
        listfiles (filefilter)

                                lists only files, directories, and parameters that match the filter criteria
                                : External filters

RandomaccessfileTools for reading and writing files

File as an array of bytes,
Use subscript to read and write byte values at specified locations

Creating objects

Randomaccessfile RAF =
New Randomaccessfile (file, "R");

R-Read Only

Randomaccessfile RAF =
New Randomaccessfile (File, "RW");

RW-Read and write

Method

Write (int b)
int four bytes, output only the end of a byte value,
[1] [2] [3] [4]–> [4]

Write (byte[] buf)
All byte values in the output array

Write (byte[] buf, int from, int length)
The length byte value in the output array from from

Read ()
Reads a byte, complements 3 0 bytes, and turns int
[4]–> [1][2][3][4]

Read end, read again, return-1

Read (byte[] buf)
Reads a batch of byte values based on the array length, and puts the array
Returns the number of bytes in this batch

Read end, read again, return-1

Seek (int position)
Locate the subscript to the specified location

Getfilepointer ()
Get the current subscript position

Writeint (int i) Full output 4 bytes of int
Writedouble (double D) Full output 8 bytes of double
...
writeUTF (String s)
Output two bytes to represent the byte length of a string
Then output the byte value of the string

READINT () reads 4 byte values into int
Readdouble () reads 8 byte values into double
...
readUTF ()
Reads 2 byte values first to determine the byte length of the string,
And then read these byte values and turn them into strings.

*) Read the end of the read, will appear eofexception

Eof-end of FILE

Flow StreamData read and write operations, abstracted into data flowing through the pipeline

The stream is one-way.

*) input stream
*) Output stream

Flows past the data, cannot repeat the flow,
Data can only be read and written from beginning to end Inputstream/outputstream

Byte Stream Abstract Parent class

Method OutputStream

Write (int b)
Write (byte[] buf)
Write (byte[] buf, int from, int length)
Flush () Brush out cached data InputStream

Read ()
Read (byte[] buf)
Available () Gets the remaining amount of readable bytes Fileinputstream/fileoutputstream

Directly to the file, read and write the data in the file

Creating objects

FileOutputStream in =
New FileOutputStream (file);

Regardless of whether the file exists,
Creates a new empty file

FileOutputStream in =
New FileOutputStream (file, true);

Not present, new;
exist, append. advanced flow, operational flow and other streams, provide specific data processing functions to the advanced flow operation, will perform the same operation to the connected stream Bufferedinputstream/bufferedoutputstream

Provides memory buffers to improve single byte read and write efficiency

Creating objects

1.BufferedOutputStream out =
New Bufferedoutputstream (phase-connected flow);

Internal Cache Array Capacity 8192

2.BufferedOutputStream out =
New Bufferedoutputstream (phase-connected flow, 16*1024);

Internal Cache Array Capacity 16k

Datainputstream/dataoutputstream

Read and write data in fixed byte format

Creating objects

DataOutputStream out =
New DataOutputStream (phase-connected flow);

Method DataOutputStream

Writeint (int i)
Writedouble (double D)
...
writeUTF (String s) DataInputStream

ReadInt ()
Readdouble ()
...
readUTF () PrintStream

Any type of data is converted to a string output

writeint
      the "
      9 '  7" ("The") ("the" "")  

Creating objects

PrintStream out = new PrintStream (phase-connected stream);

PrintStream out = new PrintStream (file);

PrintStream out = new PrintStream (file, character encoding);

Method

Print ()
println ()

Character encoding Encoding character Set Charset

Asc-ii

  0-127

Iso-8859-1
Latin-1

  160-255
  Western European character

GB2312 Double Byte
7+ in the text Fu Yi, Rong

GBK
20902 Chinese

BIG5
Jpxxx
Krxxx
Alxxx

Unicode

* Unified code, Universal Code
*) 700,000 +
*) Common characters table, double-byte
*) uncommon character tables, three bytes or more

*) Java char type with UNICODE encoding

*) UTF-8  Uni CDE Transmission Format

    *) English, single-byte
    *) Some characters, Double-byte
    *) Chinese, three bytes

Java character-coded conversion operations

*) unicode–> Other codes

  String s = "abc Chinese";
  Convert to default encoding
  byte[] A = S.getbytes ();
  Convert to UTF-8 code
  byte[] A = s.getbytes ("UTF-8");

*) Other encodings –> Unicode

  Converts a
  string s = new string (byte[] array from the default encoding);

  Converts a
  string s = new string (byte[] array, "UTF-8") from the specified encoding;

Reader/writer

Abstract parent class for character streams

Method Writer

Write (int c)
The two bytes at the end of int are a char type character,
Two byte values at the end of the output

Write (char[] buf)
Write (char[] buf, int from, int length)
Write (String s) Reader

Read ()
Read char type characters,
Two more 0 bytes into int

Read (char[] buf) inputstreamreader/outputstreamwriter

Character encoding conversion stream

OutputStreamWriter
Converts Unicode characters to other encoded byte value output

InputStreamReader
Converts the other encoded characters that are read into Unicode encoded characters

Creating objects

OutputStreamWriter out =
New OutputStreamWriter (connected byte stream);

OutputStreamWriter out =
New OutputStreamWriter (phase-connected byte stream, character encoding); Filereader/filewriter It is "file byte stream" and "encoded conversion stream"

Cannot specify character encoding, can only use default encoding

Creating objects

FileWriter out = new FileWriter (file);

Equivalent to:
OutputStreamWriter out =
New OutputStreamWriter (
New FileOutputStream (file)); Bufferedreader/bufferedwriter

Character Buffer stream

Creating objects

BufferedWriter out =
New BufferedWriter (the character stream of the phase);

BufferedReader method

ReadLine ()
Reads a line of strings without trailing line breaks

Read-end re-read, return null printwriter and printsream the same printwriter can be a stream of characters, you can also access the word throttling

PrintStream byte stream

Creating objects

1.PrintWriter out = new PrintWriter (the character stream of the phase);
2.PrintWriter out = new PrintWriter (byte stream of phase);
3.PrintWriter out = new PrintWriter (file);
3.PrintWriter out = new PrintWriter (file, encoding); Objectinputstream/objectoutputstream serialization, deserialization ObjectOutputStream
To turn an object into a sequence of byte sequences output

ObjectInputStream
Reading serialized data, recovering objects

Members that are not serialized
*) static belongs to the class and will not be serialized with the object output
*) Transient temporary,
exists in memory only while the program is running
Will not be persisted by serialization

Serializing the header byte value

*) When you create a new ObjectOutputStream object,
Automatically outputs 4 byte header values
*) When you create a new ObjectInputStream object,
Automatically reads 4 header byte values,
To confirm that the following data is the object serialization data

Serialization version number

Static final Long Serialversionuid

* Control the old version of the data,
Not allowed to revert to a new version of the type

Creating objects

ObjectOutputStream out =
New ObjectOutputStream (phase-connected flow);

Method ObjectOutputStream

WriteObject (Object obj)
Serialized output ObjectInputStream

ReadObject ()
Deserialization Read Bytearrayinputstream/bytearrayoutputstream

With an in-memory byte[] array,
Directly read and write data in an array

Creating objects

Bytearrayinputstream in =
New Bytearrayinputstream (byte[] array);

Bytearrayoutputstream out =
New Bytearrayoutputstream ();

  There is an array inside, the output data,
  placed in its internal array,
  after the output is finished, you can take out the internal array

Method Bytearrayoutputstream

Tobytearray ()
To remove an internal array