Post on 01-Jan-2021
CS111: PROGRAMMING
LANGUAGE II
Lecture 13(b): Stream & Files Computer Science
Department
Lecture Contents
dr. Amal Khalifa, 2014
Reading text files
Scanner class
Sequential Access files:
problems
Methods
objects
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How to store this data in a file?
Case study 3
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The Student class
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Data
Constructor
set methods
The Student class (cont.)
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get methods
And…
toString
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Reading text files
read data
sequentially
from a text
file using a
Scanner.
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Reading text files
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Reading text files
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File processing
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Open Read Close
Main!!
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Run!!
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Sequential Access!!
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It might be necessary to process the file sequentially
several times (from the beginning of the file) during
the execution of a program.
Class Scanner does not provide the ability to
reposition to the beginning of the file.
If it is necessary to read the file again, the
program must close the file and reopen it.
Updating Sequential-Access Files
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The data in many sequential files cannot be modified without the
risk of destroying other data in the file.
If the name “White” needed to be changed to “Worthington,”
the old name cannot simply be overwritten, because the new name
requires more space.
Fields in a text file—and hence records—can vary in size.
Records in a sequential-access file are not usually updated in place.
Instead, the entire file is usually rewritten.
Rewriting the entire file is uneconomical to update just one record,
but reasonable if a substantial number of records need to be
updated.
Refer to the book fig. 17.20 & 17.21 for more information!!
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Working on chapter 17…
That’s all for today…..
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