Java: convert List<String> to a join()d String

user_44330 0
Viewed 538095

JavaScript has Array.join()

js>["Bill","Bob","Steve"].join(" and ")
Bill and Bob and Steve

Does Java have anything like this? I know I can cobble something up myself with StringBuilder:

static public String join(List<String> list, String conjunction)
{
   StringBuilder sb = new StringBuilder();
   boolean first = true;
   for (String item : list)
   {
      if (first)
         first = false;
      else
         sb.append(conjunction);
      sb.append(item);
   }
   return sb.toString();
}

.. but there's no point in doing this if something like it is already part of the JDK.

list java string
23 Answers

With java 1.8 stream can be used ,

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

List<String> list = Arrays.asList("Bill","Bob","Steve").
String str = list.stream().collect(Collectors.joining(" and "));
user_20786720

If you're using Eclipse Collections (formerly GS Collections), you can use the makeString() method.

List<String> list = Arrays.asList("Bill", "Bob", "Steve");

String string = ListAdapter.adapt(list).makeString(" and ");

Assert.assertEquals("Bill and Bob and Steve", string);

If you can convert your List to an Eclipse Collections type, then you can get rid of the adapter.

MutableList<String> list = Lists.mutable.with("Bill", "Bob", "Steve");
String string = list.makeString(" and ");

If you just want a comma separated string, you can use the version of makeString() that takes no parameters.

Assert.assertEquals(
    "Bill, Bob, Steve", 
    Lists.mutable.with("Bill", "Bob", "Steve").makeString());

Note: I am a committer for Eclipse Collections.

Motlin_235720

Another solution, it is a variation of another answer

public static String concatStringsWSep(Iterable<String> strings, String separator) {
    Iterator<String> it = strings.iterator();
    if( !it.hasNext() ) return "";
    StringBuilder sb = new StringBuilder(it.next());
    while( it.hasNext()) {
        sb.append(separator).append(it.next());
    }
    return sb.toString();                           
}
user_9255490
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