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Split directory path with another path

I read the directory path using system properties in java which will work both in windows and Linux based systems. Now I need to split this path with only a portion of the path to retrieve the rest. eg., C:\Test1\Test2\Test3\Test4
I need to split the above path with C:\Test1\Test2 and retrieve Test3\Test4.
When I get this as string and use split function that will give me error as illegal character because of "\" character. If I plan to escape this character with "\\", this may not work in Linux box. Is there a way I can make this work both in Linux and Windows?

Use the below approach.
//Windows
String s = "C:\\Test1\\Test2\\Test3\\Test4";
String[] output = s.split(("/".equals(File.separator))? File.separator : "\\\\" );
//output: [C:, Test1, Test2, Test3, Test4]
//Linux:
String linuxString = "/Test1/Test2/Test3/Test4";
String[] linuxOutput = linuxString.split(("/".equals(File.separator))? File.separator : "\\\\" );
//output: [, Test1, Test2, Test3, Test4]
Hope this will solve the issue.

You are looking for File.separator. Use it to split your string.
From the docs,
The system-dependent default name-separator character, represented as a string for convenience.

The pattern passed to String.split has the regular expression syntax, thus the java.util.regex package is the place to look for additional tools for dealing with them, like quoting a string to enforce literal matching.
So a solution only using system properties and string operations would look like
String path=System.getProperty("your.property"), sep=System.getProperty("file.separator");
for(String s: path.split(Pattern.quote(sep)))
System.out.println(s);
However, there is no reason not to use the dedicated APIs:
Path path = Paths.get(System.getProperty("your.property"));
if(path.isAbsolute()) System.out.println(path.getRoot());
for(Path p: path)
System.out.println(p);
Note that this also handles root paths correctly, i.e. on Windows, the root of a drive is like C:\, not C:, and on Linux, the root is /, not an empty string, and both cases are not handled correctly when just splitting at the separator chars.
Even before Java 7, there was an API that could handle this:
File path = new File(System.getProperty("your.property"));
for(File f = path; f != null; f = f.getParentFile())
System.out.println(f.getName().isEmpty()? f.getPath(): f.getName());
though the code will iterate the elements in the opposite order.
Note, how simple your specific task of splitting at two levels above the path becomes with the dedicated API:
Path path = Paths.get(System.getProperty("your.property"));
Path first = path.getParent().getParent(), second = first.relativize(path);
System.out.println("first: "+first);
System.out.println("second: "+second);

You can use separator when you are building a file path.
Use java.io.File.separator

java: how to append text in a String after a certain index

i have a path
C:\Users\abc xyz\Desktop\test.docx
I want to change in into
C:\Users\sara waheed\Desktop\~$sara.docx
for that first i got the last index of backslash now i want t append '~$' after the last backslash
String str=path.toString();
int index = str.lastIndexOf('\\');
Note
I do not know the value of the path in advance
how can i achieve that

In general, you should use java.nio.file API when manipulating paths, so that it can avoid platform dependent assumptions.
String str = path.getFileName().toString();
// The string concatenation way:
if(str.endsWith(".docx")) { // should we check the beginning of fname?
// maybe it already has the prefix?
path = path.resolveSibling("~$" + str);
}
System.out.println(path);

Since you're representing files, I suggest using the Path api. You can modify any part of the path without messing with the rest.
Path file = Paths.get("C:\\Users\\abc xyz\\Desktop\\test.docx");
Path lock = file.resolveSibling("~$" + file.getFileName());
To interact with these paths, go ahead and look at the Files class.
Files.touch(lock);
Or alternatively using the classic way via path.toFile()
By the way, these are all in the java.nio.file package.

How to replace '\' with '//' in java String

For Example:
My String is:
C:\Users\Junaid\Documents\lesson2\lesson2\touchingRectangles\package.bluej
But I want it to be like this:
C://Users//Junaid//Documents//lesson2//lesson2//touchingRectangles//package.bluej

You can achieve the expected result with the following code -
path = path.replace("\\", "//");
Here the backslash() needs to be escaped by a backslash, as it throws invalid sequence error.
But honestly you don't need double front slash(//) unless you're handling anything like an URL(https://). Sometimes the filepath requires double blackslash(//) for file or stream inputs; but not always.
I would suggest you to use File.Separator instead. E.g.
String filePath = "hello" + File.separator + "world"
this gives you -"hello\world"; that is far more enough for file path manipulations.
Hope this helped :)

Is their any way to eliminate two backward slash to one in Eclipse

I came to a scenario while using eclipse, in which if i use two back slash in below mention function.
"private Keywords(){
try{
OR=new Properties();
FileInputStream fs=new FileInputStream(System.getProperty("user.dir")+"**\\src\\com\\config\\OR.properties"**);
OR.load(fs);
"
this function works but if I use single slash it won't work . Is their way that i would be able to use single backward slash only while giving a source path..

Your question has nothing to do with Eclipse.
You need to escape back-slashes in Strings, as they are themselves an escape character.
What you can eventually use to somewhat "shorten" your code is the system property System.getProperty("file.separator"), then assign it to some constant and use that reference instead.
But that's close to cosmetics.

You can use the 2 backslashes as a single variable say,
String separator = "\\";
String file_path = "src"+separator +"com"+separator +"config"+separator +"OR.properties";
System.out.println("File Path is :: " + file_path);
Or as Mena Suggested, you can use:
String separator = System.getProperty("file.separator");

Get it straight with your String literals
http://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html

Splitting filenames using system file separator symbol

I have a complete file path and I want to get the file name.
I am using the following instruction:
String[] splittedFileName = fileName.split(System.getProperty("file.separator"));
String simpleFileName = splittedFileName[splittedFileName.length-1];
But on Windows it gives:
java.util.regex.PatternSyntaxException: Unexpected internal error near index 1
\
^
Can I avoid this exception? Is there a better way to do this?

The problem is that \ has to be escaped in order to use it as backslash within a regular expression. You should either use a splitting API which doesn't use regular expressions, or use Pattern.quote first:
// Alternative: use Pattern.quote(File.separator)
String pattern = Pattern.quote(System.getProperty("file.separator"));
String[] splittedFileName = fileName.split(pattern);
Or even better, use the File API for this:
File file = new File(fileName);
String simpleFileName = file.getName();

When you write a file name, you should use System.getProperty("file.separator").
When you read a file name, you could possibly have either the forward slash or the backward slash as a file separator.
You might want to try the following:
fileName = fileName.replace("\\", "/");
String[] splittedFileName = fileName.split("/"));
String simpleFileName = splittedFileName[splittedFileName.length-1];

First of all, for this specific problem I'd recommend using the java.util.File class instead of a regex.
That being said, the root of the problem you're running into is that the backslash character '\' signifies an escape sequence in Java regular expressions. What's happening is the regex parser is seeing the backslash and expecting there to be another character after it which would complete the escape sequence. The easiest way to get around this is to use the java.util.regex.Pattern.quote() method which will escape any special characters in the string you give it.
With this change your code becomes:
String splitRegex = Pattern.quote(System.getProperty("file.separator"));
String[] splittedFileName = fileName.split(splitRegex);
String simpleFileName = splittedFileName[splittedFileName.length-1];

Another simpler way could be to do
File f = new File(path);
String fileName = f.getName();
I believe this will work provided the paths are compatible with the platform, i.e. not sure if path "c:\file.txt" will work on Linux or not.