why collections.binarysearch() returns wrong output for 1st 2 index position ?

[naved momin]

i m performing

collections.binarysearch(list,word)

on one of my arraylist , the array list has 5 word in it say
like

0 cs

1 HeadFirstJava-2ndEdition

2 Herbert_Schildt_-_Java_2_The_Complete_Reference

3 New folder

4 os by galvin

5 sample q's

when i m entering input say the words which are at index position 2 , 3 , 4 , 5 it gives me the right answer but when i enter word which at index 0 , 1 for 0 it gives -5 and for index 1 it gives -1
but i know why it is giving me this because he is not able to find the word in a list but i know this word are there in the list
what can i do to correct this ?

i know i can perform some math thing to get the right answer on this but without math can i get the right answer ?

[Matthew Brown]

A binary search assumes that your list is already sorted, otherwise the results are unpredicatable. If those are the actual contents of the list - remember that upper- and lower-case characters are sorted separately.

[Rob Spoor]

Try the other binarySearch method, with a comparator:

Collections.binarySearch(list, word, String.CASE_INSENSITIVE_ORDER)

However, keep in mind that binarySearch must use the same ordering as the array you're searching.

[naved momin]

Matthew Brown wrote:A binary search assumes that your list is already sorted, otherwise the results are unpredicatable. If those are the actual contents of the list - remember that upper- and lower-case characters are sorted separately.

thanks i got that
one more thing i want to download directory from ftp server
which means directory along with all files in that directory , i m using file tranfer mode ascii do i need to change it to some other thing to get this thing done ?

i m using libraries from apache common net

[Rob Spoor]

Naved, please start creating new threads for new problems. The latest problem has nothing to do with the binary search problem.

But to answer your questions: ASCII transfer mode should never be used for non-text files. If you have binary files you should use binary transfer mode for those. Fortunately, you can also use binary mode for text files.

[naved momin]

Rob Spoor wrote:Naved, please start creating new threads for new problems. The latest problem has nothing to do with the binary search problem.

But to answer your questions: ASCII transfer mode should never be used for non-text files. If you have binary files you should use binary transfer mode for those. Fortunately, you can also use binary mode for text files.

thanks and next time i will keep in mind