A DESCRIPTION OF THE REQUEST :
The class java.lang.String lacks a facility to merge a String array to a single String with support for a delimiter that's inserted between the array elements. This facility should be the opposite of java.lang.String.split .

JUSTIFICATION :
The String merge/join facility is very common thing and can be used in many situations. It would make the life of the majority of Java developers easier.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The best way to provide a String merge/join facility would be to implement a new String constructor with two parameters: a String array and a delimiter.

public String(String[] tokens, String delimiter)
{
// The implementation is left as an exercise to the reader ;-)
}
ACTUAL -
The following pseudo code shows how the new constructor should work :

String[] tokens = new String[]{"Hello", "World!"};

String greeting = new String(tokens, ", ");

System.out.println(greeting);

The output of the code snippet should be: Hello, World!

CUSTOMER SUBMITTED WORKAROUND :
A workaround would be to implement a helper mewthod that does the merge.
(Incident Review ID: 240506) 
======================================================================
Posted Date : 2005-07-27 04:37:46.0

N/A

I once independently suggested adding a join facility.
Given that this simple functionality gets reinvented, and
that split and join are often used in tandem, and that
perl, which was perhaps the inspiration for split, also has join,
there is strong motivation for providing join.
However, I don't think adding a constructor is a good idea.
The intent is not obvious enough.

I would favor a static method analogous to perl's

public static String join(String delimiter, String... components)

or perhaps more abstractly

public static String join(CharSequence delimiter, 
                          CharSequence... components)

This even succeeds in copying the vargarity of perl join.

  xxxxx@xxxxx   2005-04-13 20:40:04 GMT
Please refer to the forum thread on this topic for several design suggestions and two different suggested fixes.

Contribution-forum:https://jdk-collaboration.dev.java.net/servlets/ProjectForumMessageView?forumID=1463&messageID=10624
Posted Date : 2005-12-21 23:46:08.0

This is in progress for 3 years now...
PLEASE add this to next release

This is a really simple enhancement that is done over and over in many external libraries.  It's about time that it gets done...

Please add this feature!

http://forum.java.sun.com/thread.jspa?threadID=5310610&tstart=0

Yes it is a simple feature that is done in many external libraries.  It would be quite simple to add and there really isn't a reason to not have it.

Don't just accept a list of Strings, make it more general:

join(CharSequence delim, **Collection/Iterable** list)

.toString() will be called on each object in the list.

    public static <T> String joinCollection (final Collection<T> objs, String delimiter) 
    {
        if (objs == null || objs.isEmpty())
            return "";
        Iterator<T> iter = objs.iterator();
        StringBuffer buffer = new StringBuffer(iter.next().toString());
        while (iter.hasNext())
            buffer.append(delimiter).append(iter.next().toString());
        return buffer.toString();
    }

I propose the following implementation, which is both more general and slightly optimized w.r.t. joining one element collections:


    public static String join(Object delimiter, Iterable<?> elements) {
    	final Iterator<?> it;
        if (elements == null || !(it = elements.iterator()).hasNext()) {
        	return "";
        }
        final String first = it.next().toString();
        if (!it.hasNext()) {
        	return first;
        }
		final StringBuilder result = new StringBuilder(first);
        do {
        	result.append(delimiter)
        	      .append(it.next());
        } while (it.hasNext());
        return result.toString();
    }

    public static String join (Object delimiter, Object... elements) {
    	return join(delimiter, Arrays.asList(elements));
    }

We badly need high performance string concatenation in Java!