Having trouble with a .split("\\") method.

[blazedaces]

Hello again. I'm trying to take as an input an ArrayList<String> and utilize String's .spit(delimiter) method to turn that into a String[][]. I'm getting some kind of error though (I'll post the code and error lower down).

Here's a simple example:

Input ArrayList would be:
ArrayList<String> temp = new ArrayList<String>(2);
        temp.add("headerTest\\headerSectionTest\\");
        temp.add("headerTest\\start-time\\sameLastPartTest");
        temp.add("headerTest\\end-time\\sameLastPartTest");
        temp.add("DataTest\\TimeTest\\");
        temp.add("DataTest\\PieceOfDataTest\\");
 
The String[][] that I want would be (assuming my code works):
String[][] splittedStrings = new splittedStrings[temp.size()][];
splittedStrings[0] = { "headerTest", "headerSectionTest" };
splittedStrings[1] = { "headerTest", "start-time", "sameLastPartTest" };
splittedStrings[2] = { "headerTest", "end-time", "sameLastPartTest" };
splittedStrings[3] = { "DataTest", "TimeTest" };
splittedStrings[4] = { "DataTest", "PieceOfDataTest" };
 

Here's my code (main method and the table implementation method where I'm using the .spit("\\") method):

    public static void main(String args[]) {
        ArrayList<String> temp = new ArrayList<String>(2);
        temp.add("headerTest\\headerSectionTest\\");
        temp.add("headerTest\\start-time\\sameLastPartTest");
        temp.add("headerTest\\end-time\\sameLastPartTest");
        temp.add("DataTest\\TimeTest\\");
        temp.add("DataTest\\PieceOfDataTest\\");
 
        runTCW rTCW = new runTCW(temp);
        rTCW.start();
        try {
            rTCW.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
 

public MyTableModel(ArrayList<String> al) {
            numRows = al.size();
            data = new Object[numRows][numCols];
 
            String[][] tagsSeparated = new String[numRows][];
 
            for (int i = 0; i < numRows; i++) {
                tagsSeparated[i] = al.get(i).split("\\"); //This is where the error is reported, where I use the .split("\\") method
            }
 
            for (int i = 0; i < numRows; i++) {
                data[i][0] = new Boolean(true);
 
                data[i][1] = al.get(i);
 
                data[i][2] = al.get(i);
                Utilities.print(tagsSeparated[i]);
 
                data[i][3] = al.get(i);
            }
        }
 

And the error it spits out:

Exception in thread "main" java.util.regex.PatternSyntaxException: Unexpected internal error near index 1
\
 ^
    at java.util.regex.Pattern.error(Pattern.java:1700)
    at java.util.regex.Pattern.compile(Pattern.java:1453)
    at java.util.regex.Pattern.<init>(Pattern.java:1130)
    at java.util.regex.Pattern.compile(Pattern.java:822)
    at java.lang.String.split(String.java:2293)
    at java.lang.String.split(String.java:2335)
    at TagChoosingWindow$MyTableModel.<init>(TagChoosingWindow.java:210)
    at TagChoosingWindow.<init>(TagChoosingWindow.java:39)
    at runTCW.<init>(runTCW.java:14)
    at TagChoosingWindow.main(TagChoosingWindow.java:157)
 
Process completed.
 

I don't completely understand this error. Any and all help is much appreciated.

-blazed

[r035198x]

You need four backslashes to match \ because it is a special-special character.

[JosAH]

You need four backslashes to match \ because it is a special-special character.

Just to elaborate on r025198x's awfully correct and awfully terse reply:

Suppose you want to split on a single backslash; you have to escape it with
another backslash because (as r035198x already correctly wrote), the backslash
is a special character for the regular expression compiler.

If you want to supply that regular expression as a literal String, you have to get
it past the Java compiler too but javac considers a backslash character as a
special character as well, so basically you want to get two backslashes past
javac; that takes one extra backslash each:

\\\\
 

after javac munched on this string, all that is left is this:

\\
 

and this is what the regular expression compiler turns it into

\
 

I deliberately left out the double quotes for no particular reason just to emphesize
on what both compilers actually see and work on.

kind regards,

Jos

[r035198x]

Just to elaborate on r025198x's awfully correct and awfully terse reply:

Suppose you want to split on a single backslash; you have to escape it with
another backslash because (as r035198x already correctly wrote), the backslash
is a special character for the regular expression compiler.

If you want to supply that regular expression as a literal String, you have to get
it past the Java compiler too but javac considers a backslash character as a
special character as well, so basically you want to get two backslashes past
javac; that takes one extra backslash each:

\\\\
 

after javac munched on this string, all that is left is this:

\\
 

and this is what the regular expression compiler turns it into

\
 

I deliberately left out the double quotes for no particular reason just to emphesize
on what both compilers actually see and work on.

kind regards,

Jos

Don't you dare disrespect me by calling me r025198x. I've long since moved up to the r03 class.

[JosAH]

Don't you dare disrespect me by calling me r025198x. I've long since moved up to the r03 class.

Sorry, that's what your name looks like in my private unodecosimal radix number
system. It's quite a complicated system so I'll explain it some other time ;-)

kind regards,

Jos

[r035198x]

Sorry, that's what your name looks like in my private unodecosimal radix number
system. It's quite a complicated system so I'll explain it some other time ;-)

kind regards,

Jos

You need to upgrade your system then. It's probably version 0.1 and is written in Fortan right?

[blazedaces]

It worked obviously. Thank you so much for the help, both of you.

-blazed

[r035198x]

It worked obviously. Thank you so much for the help, both of you.

-blazed

One more post blazed, and you're seating pretty on 200 posts. I'll see If I can get a present for you.

[blazedaces]

One more post blazed, and you're seating pretty on 200 posts. I'll see If I can get a present for you.

It's funny you should say that, my birthday was last monday... my friends got me Frank Miller's (guy who wrote sin city comics) Comic of 300 (300 is only one digit off of 200, funny eh? Not really...). I didn't even know that movie was based on a comic. I really enjoyed it...

Anyway, ya, thanks, didn't even notice my post count was getting there...

Well to the brave 200 ... eh ... 300 ... eh ... whatever,

-blazed

[JosAH]

A bit belated but nevertheless: Happy Birthday to you.

kind regards,

Jos

[blazedaces]

A bit belated but nevertheless: Happy Birthday to you.

kind regards,

Jos

Thank you good sir.

-blazed

[hickmmi]

Thank you both for answering and explaining the problem. Saved me a lot of time!

Regards,

Matt

[r035198x]

Thank you both for answering and explaining the problem. Saved me a lot of time!

Regards,

Matt

Thanks for the thanks.