I/O ?????

1
I/O ?????

• ??? ????(I)
• ???? ???

2
stream ????

• stream
• ???? ??(source) ?? ??(destination)? ?? ?? ?? ???
  ???? ??
• ????? ????? ?? ?????? ???? ??? ?(sequence of
  bytes)??.
• ????? stream? ???? ??? ??.
• Stream programming? ??? ???? ???? ?(type)? ?? ??
  ???? ??? ?? ????? ????.
• input stream? output stream
• input stream ??? ???? ??? ?? ?? ??? ?? data?
• ?? ? ??
• output stream ??? ?? ??? ? ?? ??(??, ?? ???)?
• data? ? ? ??

3
FileInputStream FileOutputStream (1)

• FileInputStream
• ??? ??? ?? ??? FileInputStream ??? ??
• FileInputStream ???? ??? ???? ???
  FileNotFoundException? ?? ???.
• FileInputStream myStream new
  FileInputStream(C\data\aaa.txt)
• FileOutputStream
• ??? ??? ?? ??? FileOutputStream ??? ??
• ??? ?? ??? ???? ??? SecurityException? ?????.
• FileOutputStream myStream new
  FileOutputStream(bbb.txt)

4
FileInputStream FileOutputStream (2)

• import java.io. // command line
  argument? ???? ?? ?? ??
• 
  // ??? ??? copy
• public class FileCopy
• public static void main(String args) throws
  Exception
• if (args.length lt 2)
• System.out.println("Usage java CopyFile
  file1 file2")
• return
• FileInputStream fis new
  FileInputStream(args0) //???? ? ?? ?? ??
• FileOutputStream fos new
  FileOutputStream(args1) //???? ? ?? ??? ??
• int readByte 0
• while ((readByte fis.read()) ! -1)
  // EOF?? 1byte? ???
• fos.write(readByte) // 1 byte?
  ??
• fis.close()
• fos.close()
• System.out.println(args0 " copied to
  " args1)

5
DataInputStream DataOutputStream (1)

• FileInputStream, FileOutputStream - ?? byte???
  I/O? ??
• DataInputStream, DataOutputStream - ?? primitive
  I/O? ???
• 
  ??? ??
• Java? ??? ???? ?? ? 16bit-UniCode??? ??
• ??? byte ??? I/O?? ?? ?? ??? ?? ??? ??.(?? gt
  2byte)
• I/O? ? ??? 16bit-Unicode? ???? I/O class?? ????.
• Reader, Writer ????? ?? ?? ???? 2byte ????
• ???? stream

6
DataInputStream DataOutputStream (2)

• DataOutputStream Class Method summary

Method summary Method summary
writeByte(int value) Int ??? ?? ???? ???? ??.
writeBoolean(boolean value) Boolean?? true ?? 1?, false?? 0? ???? ? ??? ??? ??.
writeChar(int value) ??? ?? ? ???? ???? ??.
writeShort(int value) ??? ?? ? ???? ???? ??.
writeInt(int value) int ??? ? ??? ??? ???? ??.
writeLong(long value) Long ??? ?? ??? ??? ???? ??.
writeFloat(float value) Float ??? ? ???? ???? ??.
writeDouble(double value) Double ??? ?? ???? ???? ??.
7
DataInputStream DataOutputStream (3)

1. import java.io. //???
   ??? ???? ??? ??? ?? ??? ??
2. public class ExDataStream
3. public static void main(String args)
   throws Exception
4. if (args.length lt 1 )
5. System.out.println("???? java
   ExDataStream.java aa.txt")
6. return
8. FileOutputStream fos new
   FileOutputStream(args0)
9. DataOutputStream dos new
   DataOutputStream(fos) //privitive type size?
   i/o? ??
10. dos.writeUTF("???") // UTF-8 encoding
    ?? ??? ??
11. dos.writeUTF("41456") // UTF-8?
    16bit ????? 8bit ??? ??
12. dos.writeInt(30)
13. dos.close()
14. FileInputStream fis new
    FileInputStream(args0)
15. DataInputStream dis new
    DataInputStream(fis)
16. System.out.println("?? "
    dis.readUTF()) //??? ??? ??? ??
17. System.out.println("?? "
    dis.readUTF())
18. System.out.println("?? "
    dis.readInt())
19. dis.close()

8
reader writer

1. import java.io. //?????? ???? ?? ?? ???
   ??
2. public class StringInput
3. public static void main(String args)
   throws Exception
4. String inputString
5. InputStreamReader isr new
   InputStreamReader(System.in)
6. BufferedReader br new BufferedReader(isr)
   
7. FileOutputStream fos new
   FileOutputStream(args0)
8. OutputStreamWriter osr new
   OutputStreamWriter(fos)
9. BufferedWriter bw new BufferedWriter(osr)
   
10. inputString br.readLine()
    //readLine()? ??? ?? ??? ??? ??? ?? ? ?? ??.
12. bw.write(inputString "\n") //??? ??? ??
13. bw.close() //??? ?? stream object?
    close? ?? ?? ?? stream object? close?? ??.
14. br.close()

9
File Class

• File Class
• File Object? ???? ??? ?? ??? ?? ??? ???? ??????
  ???? ????.
• File Object? ?? ?? ??? ????? ??? ? ??.
• ???? ?????? ???? ???? ??? ?? ? ?? ???, ?? ??? ???
  ? ? ?? ?? ?? ???? ????.

Method summary Method summary
exists() File ??? ???? ???? ????? ???? true, ??? false ??
isDirectory() File ??? ????? ???? true, ??? false ??
isFile() File ??? ??? ???? true, ??? false ??
canRead() File ??? ???? ??? ?? ? ??? true, ??? false ????. ??? ?? ?? SecurityException? ???? ? ??.
canWrite() File ??? ???? ??? ? ? ??? true, ??? false ?? ??. ??? ? ? ??? SecurityException? ???? ? ??.
10
URL Class

• URL Class
• Java.net ???? ?? ?? ??.
• URL??? ?? URL? ?? ??? ??? ???, ???? ??? ??? ???
  ????? ?? ? ??.
• URL? ???? ??? ???? ??? ??? ???? ? ? ??.
• ??? ?? URL? local pc? ???? ?? ? ??.
• import java.io. // ???
  ?? ??? ???? ???? ??
• import java.net. //URL
  Class?????? ??? import??.
• public class GetIndexHtml
• public static void main(String args)
  throws Exception
• byte inputString new byte1024
• InputStream is (new URL(args0)).openS
  tream()
• FileOutputStream fos new
  FileOutputStream(args1)
• while(is.read(inputString, 0,
  inputString.length) ! -1)
• fos.write(inputString)
• fos.close()

11
RandomAccessFile(1)

• RandomAccessFile
• ??? ??? ???? ? ??
• ???, ?? ????? ??? ??? ??? ? ?? ??(RandomAccess)?
  ??
• RandomAccessFile raf new
  RandomAccessFile("c\myfile.txt", "r/w")

Method summary Method summary
seek(long pos) ??? ?? ??? pos ??? ??? ??? ???
getFilePointer() ??? ?? ??(??? ??????? ??)? long ???? ????.
length() ??? ??? ??? ??? long ????? ????.
12
RandomAccessFile(2)

• import java.io.
• import java.util.
• public class RandomWrite
• public static void main(String args)
  throws Exception
• RandomAccessFile raf new
  RandomAccessFile("Mylog.log", "rw")
• raf.seek(raf.length()) //??? ?? ?????
  ?? ??? ???.
• raf.writeUTF(new Date().toString())
  //?? ??? ??.
• raf.close()

13
Serialization(1)

• Serialization
• ??? ?? ??? ???? ?? ?? ??
• ???? ???? ?? ??? type ???? ?? ???? ???? ?? ?? ?
  ?? ??? ??
• serializable? ? ? ?? object? class?
  Serializable??? ?? interface? ??? implements??
  ??.
• Serializable interface
• serializable interface implements? method? ??.
• Serializable? implements??? ?? ?
  class?serializable? ????? ????.
• Object? serialization? ? data??(member??)? ????
  constructor? method? code? ???? ???.

14
Serialization(2)

1. import  java.io. //primitive
   type? ?? object? ??? ?? ?? ??
2.  public class TestSerialization implements
   Serializable
3.          String name
4.           int age 7
5.          TestSerialization (String name, int age)
   
6.                       this.name name
7.                       this.age age
8.       

• public class SerializeMyObject
  //TestSerialization class? object? ??? write??
•             TestSerialization ts
•               public static void main(String
  args) throws Exception
•                           SerializeMyObject smo
  new SerializeMyObject()
•                           smo.writeMyObject()
  // object? file? write?.
•                           smo.ts null
  // object? memory?? ??.
•                           smo.readMyObject()
  // ???? object? ?? ???.
•                           System.out.println(smo.t
  s.name)
•               

15
Serialization(3)

•        public void writeMyObject() throws
  Exception //object? ??? write
•                  ts new TestSerialization("???",
  32)
•                  ObjectOutputStream oos
•                   new ObjectOutputStream(new
  FileOutputStream("myObject.txt"))
•                   oos.writeObject(ts) // object?
  ??? write?.
•                   oos.close()
•         
•  
•         public void readMyObject() throws
  Exception // ??? ??? object? ??
• 
  
  //???? ??? ???
•                  ObjectInputStream ois
•                  new ObjectInputStream(new
  FileInputStream("myObject.txt"))
•                  ts (TestSerialization)ois.readO
  bject() // object? ???? ??? memory? ??.
•                  ois.close()
•