Writing Files - Beginning Java 2 SDK - page 423

A view buffer is a buffer that allows the data in a backing byte buffer to be viewed as being of
a particular basic type.

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You insert data into a buffer using its put() methods and retrieve data from it using its
get() methods. Relative get() and put() methods increment the buffer's position,
whereas absolute get() and put() methods do not.

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You write the contents of a ByteBuffer object to a file using a write() method belonging
to the FileChannel object for the file.

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The amount of data transferred between a buffer and a file in an I/O operation is determined
by the buffer's position and limit. Data is read or written starting at the file's current position.

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You can lead a horse to water but you can't make him drink.

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Exercises

1. Modify the example that writes proverbs to a file to separate the proverbs using a delimiter
character. You will need to choose a delimiter character that will not appear in normal text.

2.

Write a program that, using an integer array of date values containing month, day, and year as
integers for some number of dates (10 say, so the int array will be two dimensional with 10
rows and 3 columns), will write a file with a string representation of each date written as
Unicode characters. For example, the date values 3,2,1990 would be written to the file as 2nd
March 1990 . Make sure that the date strings can be read back, either by using a separator
character of some kind to mark the end of each string, or write the length of each string before
you write the string itself.

3.

Extend the previous example to write a second file at the same time as the first, but containing
the month, day, and year values as binary data. You should have both files open and be
writing to both at the same time.

4.

Write a program that, for a given String object defined in the code, will write strings to a file
in the local character encoding (as bytes) corresponding to all possible permutations of the
words in the string. For example, for the string, the fat cat , you would write the strings:
the fat cat , the cat fat , cat the fat , cat fat the , fat the cat , fat cat the , to
the file, although not necessarily in that sequence. (Don't use very long strings; with n words
in the string, the number of permutations is n! ).