Java Reference
In-Depth Information
Display 10.22
Random Access to a File
(part 2 of 2)
40
System.out.println("Returning to location 3,");
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System.out.println("where we wrote the double.");
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ioStream.seek(3);
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double
oneDouble = ioStream.readDouble();
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System.out.println("The double value at location 3 is "
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+ oneDouble);
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ioStream.close();
The location of
readDouble
must be a location where
writeDouble
wrote to the file.
47
}
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catch
(FileNotFoundException e)
49
{
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System.out.println("Problem opening file.");
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}
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catch
(IOException e)
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{
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System.out.println("Problems with file I/O.");
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}
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System.out.println("End of program.");
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}
The dialog assumes the file
bytedata
did
not exist before the program was run.
58
}
Sample Dialogue
Writing 3 bytes to the file bytedata.
The length of the file is now = 3
The file pointer location is 3
Moving the file pointer to location 1.
The value at location 1 is 2
The value at the next location is 3
Now we move the file pointer back to
location 1, and change the byte.
The value at location 1 is now 9
Now we go to the end of the file
and write a double.
The length of the file is now = 11
Returning to location 3,
where we wrote the double.
The double value at location 3 is 41.99
End of program.
Byte locations are numbered
starting with zero.
Three 1-byte values and one
double
value that uses 8 bytes = 11 bytes
total.
