A method to reverse effect of java String.split()?

Question

I am looking for a method to combine an array of strings into a delimited String. An opposite to split(). I've seen this in other languages.

Wanted to ask the forum before I try writing my own( since the JDK has everything...)

Thanks,

Answer 1

There's no method in the JDK for this that I'm aware of. Apache Commons Lang has various overloaded join methods that do what you want.

Answer 2

There are several examples on DZone Snippets if you want to roll your own that works with a Collection. For example:

public static String join(AbstractCollection<String> s, String delimiter) {
    if (s == null || s.isEmpty()) return "";
    Iterator<String> iter = s.iterator();
    StringBuilder builder = new StringBuilder(iter.next());
    while( iter.hasNext() )
    {
        builder.append(delimiter).append(iter.next());
    }
    return builder.toString();
}

Answer 3

I got the following example here

/*
7) Join Strings using separator >>>AB$#$CD$#$EF

 */

import org.apache.commons.lang.StringUtils;

public class StringUtilsTrial {
  public static void main(String[] args) {

    // Join all Strings in the Array into a Single String, separated by $#$
    System.out.println("7) Join Strings using separator >>>"
        + StringUtils.join(new String[] { "AB", "CD", "EF" }, "$#$"));
  }
}

Answer 4

Google also provides a joiner class in their Google Collections library:

Joiner API

Google Collections

Answer 5

Based on all the previous answers:

public static String join(Iterable<? extends Object> elements, CharSequence separator) 
{
    StringBuilder builder = new StringBuilder();

    if (elements != null)
    {
        Iterator<? extends Object> iter = elements.iterator();
        if(iter.hasNext())
        {
            builder.append( String.valueOf( iter.next() ) );
            while(iter.hasNext())
            {
                builder
                    .append( separator )
                    .append( String.valueOf( iter.next() ) );
            }
        }
    }

    return builder.toString();
}