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Published bySamuel Stevenson Modified over 9 years ago
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IB103 Week 10 Files CHAPTER 19
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Files RAM vs. Files of CD or HD Fasterslower Costs morecheaper Temporarypermanent Stores whilecopied to RAM to Executingexecute Size 32, to 128, 256…floppy 1.4M CD 650 MB, HD Billions Bytes
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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
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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
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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
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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
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FileDemo1 try{ outFile = new PrintWriter( new FileWriter("testout.txt"), true); outFile.print(inputTextArea.getText() ); outFile.close(); }
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FileDemo1 part 2 catch (IOException e) { System.err.println("File Error: " + e.toString() ); System.exit(1); }
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The System Class.in,.out,.err (input/output/error) Command Line Input/ Output Java Console
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