combine string[] into string like perl's join function

[tekberg]

I'm looking for a way to combine elements of a string array (or object.toString()s) into a single string. More specifically is there is a Java method or simple combination of methods, that can perform this kind of join in a single expression?

I'm not looking for this:

public static String join(String delimiter, Object[] array) {

StringBuilder sb = new StringBuilder();
boolean firstTime = true;
for(Object element: array) {

if (firstTime)

firstTime = false

else

sb.append(delimiter);

sb.append(element.toString());

}
return sb.toString();

}

I'm looking for something like this:

String foo = array.join(",");

I've looked in Java 6's Collections, Arrays and String classes with no luck.

--tom

[Eranga]

As far as I know there is no simple way to add element into a single string object. Easiest way to do this is, loop through the array and concat each element of the array in to previous one.

[CJSLMAN]

Maybe something like this:

String daString;
for (int i = 0; i < daArray.length; i++)
    {
      daString += daArray[i];
     }

Luck,
CJSL

[tekberg]

The simplest example of what I'm looking for is this:

     public static void main(String[] args) {
         final String[] array = new String[]{"one", "two", "three", "four"};
         String s = new Scanner(
                     new Readable() {
                         private int i = 0;
                         public int read(CharBuffer ch) {
                             return (i < array.length)
                                         ? ch.append(array[i++]).length()
                                         : -1;
                         }
                     }
             ).useDelimiter("\\Z").next();
         System.out.println(s);
     }

The output is onetwothreefour.

The problems are that the string array has to be final, and it is hardcoded in the read method.

[CJSLMAN]

Not sure how you can get an output, because the above code doesn't compile.

String s = new Scanner(...

Instantiating the Scanner class doesn't return a String. It's supposed to create an instance of the scanner class.

I'm not sure what you want to do and I'm not sure what the problem is. Maybe you could try to explain again. I also don't see the relationship between the initial question and the posted code.

Luck,
CJSL

[tekberg]

You have to look at the end of the expression to see how a String is generated. There are 3 expressions nested together. First a Scanner object is created. Second the 'useDelimiter' method sets the delimiter to EOF and returns the same Scanner object. Third the 'next' method scans the whole thing and returns a String.

[angryboy]

but how is this simpler than CJSLMAN's example?

[CJSLMAN]

Oh... OK... the way it's coded, I didn't catch that. For some crazy and unknown reason, the complier was giving me a couple of errors. I saved the program again and it worked (go figure). and yes I get your result as an output.

Sorry, but I still don't understand what the problem is. You want the output to be "one two three four" ?

Luck,
CJSL

[Eranga]

Maybe something like this:

String daString;
for (int i = 0; i < daArray.length; i++)
    {
      daString += daArray[i];
     }

Luck,
CJSL

This is the way I suggest to workout. I don't think there is any other way than simpler this.

[CJSLMAN]

Eranga... that's what I keep on thinking... unless the OP has some requirement that I'm not seeing....

CJSL