Java program file I/O

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ឣ្នកវណ្នំា: រោក ោង រ៊ុន ៉េ៊ុង
រោក លន់ ស៊ុែត្ថា ន
រោក រេង ត៊ុោ
រោក ដារ៉េ រេញចិតត

ថ្នន ក់ រសៀមររ ប្ក ុមទី ៣
ប្រធានរទ៖ FileI/O
សមាជ្ិក
1. លោក លន់ សុវត្ថា នា
2. លោក ផ៉ា ន់ ភីរ៉ង់
3. លោក អាំង តឹកជុន
4. កញ្ញា ល ៀត ម៉ា និត

មាតិកា
1. Path Class/File Class
2. Read/Write File
3. FileInputStream/FileOutputStream
4. FileReader/FileWriter
3
5. InputStream/OutputStream
6. InputStreamReader/OutputStreamWriter
7. Serialization
8. Random Access

1. Path Class and File Class
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• Path Class គឹជា class មួយដែលផ្ទុកទៅទោយ method សម្រាប់ទ្វើការ ជាមួយ information របស់ Path ទៅកនុង File
System ។ Path object ាន file name និង directory list សម្រាប់ ការបទងកើត Path, ការោក់ទីតាំង file និង ម្រតួតពិនិ
តយ file/directory។
Method and Description
get(String first, String... more) Converts a path string, or a sequence of strings that
when joined form a path string, to a Path.
get(URI uri) Converts the given URI to a Path object.

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• Create Path
import java.io.file.Path;
import java.io.file.Paths;
public class CreatePath {
private Path path; // instance variable
public static void main (String [] args) {
CreatePath example = new CreatePath();
example.createPath();
}
private void createPath() {
path = Paths.get("D:JCGarticlesPathfile1.txt");
System.out.println("Path created: " + path.toString());
}
}

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• Java File Class ទម្របើទែើមបីទ្វើការជាមួយ file និង directory pathnames។ ទ ើយការរបស់វាគឹសម្រាប់ បទងកើត files និង
directories, file searching, file deletion .
S.N. Constructor & Description
1 File(File parent, String child)
This method creates a new File instance from a parent abstract pathname and a child pathname string.
2 File(String pathname)
This method creates a new File instance by converting the given pathname string into an abstract
pathname.
3 File(String parent, String child)
This method creates a new File instance from a parent pathname string and a child pathname string.
4 File(URI uri)
This method Creates a new File instance by converting the given file : URI into an abstract pathname.

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• Create New file “test.txt”
import java.io.File;
public class CreateFile {
public static void main(String[] args) {
try {
File new_file = new File("test.txt");
} catch (Exception e) {
e.printStackTrace();
}
}
}

2. Read/Write File
8
 Read File : ដាំល ើរការអនទិននន័យពីFile
 Write File : ដាំល ើរការសរលសរ/ល ោះទិននន័យពីFile

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Read/ write File មន:
• Read/Write all Bytes or Line from/to File : for small file
2. Read/Write File

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• Read/Write File Using Buffer Stream I/O : Read/Write TEXT from/to File
• Read/Write File Using Stream I/O : Read/Write BYTE stream from/to File
• Read/Write File Using Channel I/O : Read/Write TEXT from/to File
(Channel I/O read/write a buffer at a time)
2. Read/Write File

3. FileInputStream / FileOutputStream
11
FileInputStream គឺជា Class មួយដដលល្រើសាំរារ់ Read file ជា Byte Stream. លៅកន ុង FileInputStream មន
SubClass មួយលទៀតល្ម ោះ ថា InputStream. ចាំ ដនក FileOutputStream គឺជា Class មួយដដលល្រើសាំរារ់ Write
File ជា Byte Stream. លៅកន ុង FileInputStream មន SubClass មួយលទៀតល្ម ោះថា OutputStream.

3. FileInputStream / FileOutputStream
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Method សំាខាន់ៗ រស់ FileInputStream/FileOutputStream
• int available() ជាMethod មួយដដលវាល្វើការពិនិតយ លមើលថាអចRead នឬ ត់លរើវា Read នលនាោះ return
true ដតលរើវាមិនអច Reader នលនាោះវា Return false.
• void close() ជា Method មួយដដល closes file input stream ល ើយនិង resources លសេងលទៀតដដលមនទាំនាក់
ទាំនង និងstream.
• int read() ជា method reads a byte of data from this input stream.

4. FileReader / FileWriter
13
• FileReader (java.io.Reader)គឺជា base class សាំរារ់ Read subclasses in the Java IO API. FileReader
• វាក៏ដូចលៅនិង InputStreamReader ដតវាខុសគ្នន ្តង់ថា FileReader ល្វើការRead ជាText ដត
InputStreamReader វាRead ជា Byte Stream
• ចាំ ដនក FileWriter (java.io.Writer) គឺជា base class សាំរារ់ Write subclasses in the Java IO API
FileWriter វាក៏ដូចលៅនិង InputStreamWriter ដតវាខុសគ្នន ្តង់ថា FileWriter ល្វើកាWrite ជាText
ដតInputStreamReader វាWriteជា Byte Stream.

4. FileReader / FileWriter
14
FileReader
FileWriter

5. InputSream / OutputStream
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Java Application ល្រើ្ ស់ input stream លដើមបីល្វើការ read data ពី source និង ល្រើ្ ស់ output stream
លដើមបីល្វើការ write data លៅកាន់ destination។
InputStream Class and OutputStream Class:គឺជា abstract class ដដលជា subclass ររស់ classes ទាំង ស់
ដដលតាំណាងលអយ input stream ររស់ bytes
ដំារណ្ើ កា រស់ inputstream និង outputstream
Method of InputStream Method of OutputStream
1) public abstract int read()throws
IOException:
1) public void write(int)throws IOException:
2) public int available()throws IOException: 2) public void write(byte[])throws IOException:
3) public void close()throws IOException: 3) public void close()throws IOException:

5. InputSream / OutputStream
16
Hairachy of InputStream/OutputStream

6. InputSreamReader/OutputStreamWriter
17
Java.io.InputStreamReader class គឺជាស្ពា នចមលងពី byte streams លៅកាន់ character streams
វាល្វើការ read ពី byte ល ើយ decode ជា character លោយល្រើ្ ស់ charset
ចាំ ដនកJava.io.OutputStreamWriter វាល្វើការ write ល ើយ encode លៅជា byte វ ញ លោយល្រើ្ ស់ charset។
S.N. InputStreamReader: Constructor & Description OutputStreamWriter: Constructor & Description
1 InputStreamReader(InputStream in)
This creates an InputStreamReader that uses the default charset.
OutputStreamWriter(OutputStream out)
This creates an OutputStreamWriter that uses the default character
encoding.
2 InputStreamReader(InputStream in, Charset cs)
This creates an InputStreamReader that uses the given charset.
OutputStreamWriter(OutputStream out, Charset cs)
This creates an OutputStreamWriter that uses the given charset.
3 InputStreamReader(InputStream in, CharsetDecoder dec)
This creates an InputStreamReader that uses the given charset
decoder.
OutputStreamWriter(OutputStream out, CharsetEncoder enc)
This creates an OutputStreamWriter that uses the given charset
encoder.
4 InputStreamReader(InputStream in, String charsetName)
This creates an InputStreamReader that uses the named charset.
OutputStreamWriter(OutputStream out, String charsetName)
This creates an OutputStreamWriter that uses the named charset.

7. Serialization
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• Serialization គឺជាម៉ា សុីន ននការ សរលសរនូវ State នន Object លៅជា Byte stream.
• ្ពមទាំងការលៅនូវ Serialization លនោះមកវ ញ ល្រើ្ ស់លៅថា Deserialization.
• String class និង wrapper class ទាំង ស់្តូវា ន implements ពី java.io.serializable interface
លោយ default.
• Classes ObjectInputStream and ObjectOutputStream គឺជា high-level stream ដដលវាមនសទ ុក
នូវ method សាំរារ់ Serialization និង Deserialization ររស់ Object.
• Method write Object ដដលលគនិយមល្រើ៖
• Method serialization និង deserialization Object ដដលលគនិយមល្រើ៖

7. Serialization
19
Example:
Example Serilization Object :

7. Serialization
20
Example Deserializing an Object:

8. RandomacessFile
21
Java.io.RandomAccessfile class វា្ាររីដូចជា Array យ៉ា ង្ាំមួយដដល សទ ុកជា bytes លៅកន ុង file
ដដល វាអចទទូល នទាំង reaing និង writing លៅជា random access file.
Class constructor:Constructor Descriptio
RandomAccessFileFilefile, Stringmode This creates a random access file stream to read from, and optionally to
to, the file
specified by the File argument.
RandomAccessFileFilefile, Stringmode This creates a random access file stream to read from, and optionally to
to, a file
with the specified name.

8. RandomacessFile
22
Methods Descriptio
void close This method Closes this random access file stream and releases any system
associated with the stream.
FileChannel getChannel This method returns the unique FileChannel object associated with this file.
FileDescriptor getFD This method returns the opaque file descriptor object associated with this stream.
long getFilePointer This method returns the current offset in this file.
long length This method returns the length of this file.
int read This method reads a byte of data from this file.
int readbyte[]b This method reads up to b.length bytes of data from this file into an array of bytes.
int readbyte[]b, intoff, intlen This method reads up to len bytes of data from this file into an array of bytes.
boolean readBoolean This method reads a boolean from this file.
byte readByte This method reads a signed eight-bit value from this file.

8. RandomacessFile
23
• Example:
Result:
Hello world
Closing Stream....
Stream Closed.

8. RandomAcessFile
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S.N. InputStreamReader: Method & Description OutputStreamWriter: Method & Description
1 void close()
This method closes the stream and releases any system resources
associated with it.
void close()
This method closes the stream, flushing it first.
2 String getEncoding()
This method returns the name of the character encoding being used by
this stream
String getEncoding()
This method returns the name of the character encoding being used by
this stream.
3 int read()
This method reads a single character.
void write(char[] cbuf, int off, int len)
This method writes a portion of an array of characters.
4 int read(char[] cbuf, int offset, int length)
This method reads characters into a portion of an array.
void write(int c)
This method writes a single character.
5 boolean ready()
This method tells whether this stream is ready to be read.
void write(String str, int off, int len)
This method writes a portion of a string.

9. ប្រភេឯកសា
• http://www.tutorialspoint.com/java/io
• http://www.tutorialspoint.com/java/java_files_io.htm
• https://docs.oracle.com/javase/7/docs/api/java/nio/file/Paths.htmll
• https://examples.javacodegeeks.com/core-java/nio/file-nio/path/java-nio-file-path-example/
• https://docs.oracle.com/javase/tutorial/essential/io/file.html
• http://www.tutorialspoint.com/java/java_files_io.htm
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Java program file I/O

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