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Best way to store words for given scenerio

I am working on Java project [Maven].
I am confused in one point. I don't know what is logiclaly corect.
Problem is as follows :-
Sentence is given, and from their I have extract some particular words.
Solution that I found
I make one regex and put in Constants class. Whenever I have to add more words, I simply appended words in regex.
This solves the problem.
I am confused here
I am thinking, if I put numbers of text files in resources folder where each text file denotes one regex expression.
REGEX = (?:A|B|C|D)
A, B, C, D = Word(String)
Is it a good idea ? If not please suggest any other.

Why would you save regex's in a text file? The fact that you're using a regex seems like an implementation detail that you would want to encapsulate (unless you want the significantly greater functionality but also overhead of supporting regexes).
Also, why do you need new files for each word? That seems like you could just have one file with a word per line that is all of the words you're interested in. This would be much more simple for a user to understand than 100 files with one regex per file.

As my understanding, you want to find some key words from the input string. And those key words could be extened according your requirments.
your current solution is to make this regex (?:A|B|C|D) in your Constant class, wheneveer it's required, you'll add more key words in this regex.
If my understanding is not wrong, maybe, one suggestion is to put this regex in your properties file, like this
REGEX = (?:city|Animal|plant|student)
if too long, it's could be like this
REGEX = (?:city|Animal|plant|student|car|computer|clothes|\
furnature|others)
Your second idea, if my understanding is not wrong, is to put the keywords as the file name, and those files are put in one resource folder. therefore, you could obtain those files name to compose the final regexp. If your regex are always fixed as the (?:A|B|C|D) format, then this solution is good & convenient. (Every time, you add one new keyword file, you don't need to modify any source code & property file)

How to escape forward slash in java so that to use it in path

I am trying to escape forward slash in String which can be used in path using Java.
For example: String:: "Test/World"
Now I want to use above string path.At the same time I have to make sure that "Test/World" will come as it is in path. Sorry if its duplicate but I couldn't find any satisfactory solution for this.
My purpose is to use above string to create nodes in Zookeeper.
Example:
If I use following string to create node in Zokkeeper then I should get "Test/World" as a single node not separate. Zookeeper accepts "/" as path separator which in some cases I dont require.
/zookeeper/HellowWorld/Test/World
Thanks

You should know about File.separator ... This is safer than \ or / because Linux and Windows use different file separators. Using File.separator will make your program run regardless of the platform it is being run on, after all, that is the point of the JVM. -- forward slash will work, however, File.separator will make you end users more confident that it will.
And you don't need to escape "/ ... you should also see the answer to this question
String fileP = "Test" + File.separator + "World";

In order to escape a character in Java use "\"
for example:
String strPath = "directory\\file.txt".
I believe you do not need to escape forward slashes such as: "/"

Let me rephrase your question. You are trying to create a node in zookeeper and it should be /zookeeper/HelloWorld/NodeName. But the last part "NodeName" is actually "Test/World", and you are looking for ways to escape "/" so the node name can be "Test/World".
I don't think it would work escaping the char, unless you tried with unicode.
Try \u002F which is the equivalent for /.

We are trying to solve exactly the same problem (using filesystem path as node name in zookeeper) a we haven't found a way how to have '/' in node name.
Solution would be either to replace '/' with some character, that cannot appear in your node name. For paths that would be '/' or '\0', which wont help us in this case.
Other possibility is to replace '/' with string of characters allowed in node name, e.g. "Test/World" -> "Test%#World", "Test%World" -> "Test%%World" and add escaping/de-escaping to saving and loading.
If there is any more straightforward way, I'd love to hear it.

I don't know anything about Zookeeper. But it looks to me as though you're trying to keep a list of strings like "zookeeper", "HellowWorld", "Test/World", that you then want to use either to create Zookeeper nodes or to create a pathname in a file system. (I'm assuming that if you're working with a file system, you're going to have a subdirectory Test and a file or subdirectory World in the Test subdirectory. If you're actually trying to create a single file or directory named Test/World, give up. Both Linux and Windows will fight with you.)
If that's the case, then don't try to represent the "path" as a simple String that you pass around in your program. Instead, represent it as a String[] or ArrayList<String>, and then convert it to a filesystem path name only when you need a filesystem path name. Or, better, define your own class with a getFilesystemPath method. Converting your list of node names to a pathname String too early, and then trying to reconstruct the list from the String later, is a poor approach because you throw away data that you need later (in particular, you're throwing away information about which / characters are separators and which ones are part of node names).
EDIT: If you also need a single path name for Zookeeper, as you mentioned in another comment, I can't help you since I don't know Zookeeper and haven't found anything in a quick look at the docs. If there is a way to escape the slash for Zookeeper, then I still recommend defining your own class, with a getFilesystemPath method and a getZookeeperPath method, since the two methods will probably return different Strings in certain cases. The class would internally keep the names as an array or ArrayList.

Using regex to match String to name in external file

I am writing a program that is supposed to detect whether a type name is contained within an external file. For example, if a string is equal to "anitasugarland" and the external file contains the name "ANITA" then is there any way to confirm if there is a name match? The problem I'm having is if I just use Java's "startsWith" then it matches on other names like "An" or other names. As you can see this can cause inaccuracies. So is there a way using regex or word boundaries to check if a first name in the string matches the one in the external file? As of now this really has me stumped. If someone could take a look at this or provide a possible solution I would very much appreciate it!
Thank you!

Java two dots at the end of a path have unexpected results

I've run into what I thought was unusual behavior when working with some File objects.
import java.io.File;
public class MyClass
{
public static void main(String[] args)
{
File file = new File("C:\\x..");
System.out.println(file.isDirectory());
System.out.println(file.listFiles());
}
}
Assuming that some directory C:\x exists, file.isDirectory() will return true with the added two dots at the end of the path. This replicates the behavior in the command line, where cd x.. will change the directory to x.
However, when calling file.listFiles(), the method returns null, which is only supposed to happen if the file is not a directory. This seems to be inconsistent with the definition of the listFiles().
Why is this so? And why does having two dots at the end of the path go to the same directory as if there was no dots?
This problem seems to be exclusive to Windows. Linux correctly (?) returns false for isDirectory().

Windows trims trailing dots from path and filenames. I am unable to find a concrete reference for this, it's just one of those mysterious things that has always been that way.
It trims the trailing dots from the full pathname, not the individual components.
Therefore, while "C:\x...." is the same as "C:\x", "C:\x....\filename" is not the same as "C:\x\filename", as the latter does not have trailing dots.
You would have to look at the JDK's native FileSystem source on Windows to see precisely how it is obtaining a list of files, but I suspect it's doing some kind of search on e.g. "C:\x..\*.*" using Windows' FindFirstFile API call or something, where the dots are no longer trailing. In other words, presuming "C:\x" is a directory, while the path "C:\x.." is a directory, "C:\x..\*.*" matches nothing, and "C:\x..\subdirectory" does not map to "C:\x\subdirectory".
You should avoid using such paths. I'm not sure how you obtained that path string in the first place.
You can use File.getCanonicalPath() or File.getCanonicalFile() to convert it back to a more useable pathname.
By the way, if you want to have some fun with Windows, type the following in a command prompt (assuming "c:\windows\temp" exists, otherwise replace with some other path):
echo > \\?\c:\windows\temp\x.
The \\?\ prefix in Windows disables filename processing and expansion. Now delete the resulting file. Try it in Explorer too.
Spoiler:
You'll have to delete it with a wildcard from the console, e.g. del x?

You forgot to add extra slashes before .. to it should be c:\\x\\... This will point you to C: indeed

Detect when file can't be created because of bad characters in name

Can anyone tell me how to cope with illegal file names in java? When I run the following on Windows:
File badname = new File("C:\\Temp\\a:b");
System.out.println(badname.getAbsolutePath()+" length="+badname.length());
FileWriter w = new FileWriter(badname);
w.write("hello world");
w.close();
System.out.println(badname.getAbsolutePath()+" length="+badname.length());
The output shows that the file has been created and has the expected length, but in C:\Temp all I can see is a file called "a" with 0 length. Where is java putting the file?
What I'm looking for is a reliable way to throw an error when the file can't be created. I can't use exists() or length() - what other options are there?

In that particular example, the data is being written to a named stream. You can see the data you've written from the command line as follows:
more < .\a:b
For information about valid file names, look here.
To answer your specific question: exists() should be sufficient. Even in this case, after all, the data is being written to the designated location - it just wasn't where you expected it to be! If you think this case will cause problems for your users, check for the presence of a colon in the file name.

I would suggest looking at Regular Expressions. They allow you to break apart a string and see if certain characteristics apply. The other method that would work is splitting the String into a char[], and then processing each point to see what's in it, and if it's legal... but I think RegEx would work much better.

You should take a look at Regular Expressions and create a pattern which will match any illegal character, something like this:
String fileName = "...";
Pattern pattern = Pattern.compile("[:;!?]");
Matcher matcher = pattern.match(fileName);
if (matcher.find())
{
//Do something when the file name has an illegal character.
}
Note: I have not tested this code, but it should be enough to get you on the right track. The above code will match any string which contains a :, ;, `!' and '?'. Feel free to add/remove as you see fit.

You can use File.renameTo(File dest);.

Get the file name first:
String fileName = fullPath.substring(fullPath.lastIndexOf('\\'), fullPath.length);
Create an array of all special chars not allowed in file names.
for each char in array, check if fileName contains it. I guess, Java has a pre-built API for it.
Check this.
Note: This solution assumes that parent directory exists