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IB103 Week 10 Files. CHAPTER 19. Files. RAM vs. Files of CD or HD Faster slower Costs more cheaper Temporary permanent Stores while copied to RAM to Executing execute Size 32, to 128, 256… floppy 1.4M CD 650 MB, HD Billions Bytes.

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Ib103 week 10 files

IB103 Week 10Files

CHAPTER 19


Files
Files

  • RAM vs. Files of CD or HD

  • Faster slower

  • Costs more cheaper

  • Temporary permanent

  • Stores while copied to RAM to

    • Executing execute

  • Size 32, to 128, 256… floppy 1.4M

    • CD 650 MB, HD Billions Bytes


Files security and applets
Files security and Applets

  • Downloaded from a web page run via java enabled browser or appletviewer on users PC. (security rules for applets in Java – very strict, examples can not read, write to local files only communicate with original server etc. by default


Streams bytes continuous
Streams – bytes continuous

  • Essentials of streams: (In)

  • 1. Open file

  • 2. Read data into variables

  • 3. Close file

  • (Out)

  • 1. Open file

  • 2. Output/write items in required sequence

  • 3. Close file


Buffer a chunk of memory
Buffer – a “chunk” of memory

  • “Spoon fed” to a device, like a printer that is much slower that CPU. The CPU can is then free to run full speed until another buffer full is needed by the device


File example in text filedemo1
File example in text “FileDemo1”

  • File input See “FileDemo1”

  • File Search See “FileSearch” – seeks a string within the file

  • “FileDialog” “gets” a file, uses a window with a “load” button


Filedemo1
FileDemo1

try{

outFile = new PrintWriter( new FileWriter("testout.txt"), true);

outFile.print(inputTextArea.getText() );

outFile.close();

}


Filedemo1 part 2
FileDemo1 part 2

catch (IOException e) {

System.err.println("File Error: " +

e.toString() );

System.exit(1);

}


The system class
The System Class

  • .in, .out, .err (input/output/error)

  • Command Line Input/ Output

  • Java Console


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