Last iteration of enhanced for loop in java

Another alternative is to append the comma before you append i, just not on the first iteration. (Please don't use "" + i, by the way - you don't really want concatenation here, and StringBuilder has a perfectly good append(int) overload.)

int[] array = {1, 2, 3...};
StringBuilder builder = new StringBuilder();

for (int i : array) {
    if (builder.length() != 0) {
        builder.append(",");
    }
    builder.append(i);
}

The nice thing about this is that it will work with any Iterable - you can't always index things. (The "add the comma and then remove it at the end" is a nice suggestion when you're really using StringBuilder - but it doesn't work for things like writing to streams. It's possibly the best approach for this exact problem though.)

Another way to do this:

String delim = "";
for (int i : ints) {
    sb.append(delim).append(i);
    delim = ",";
}

Update: For Java 8, you now have Collectors

It might be easier to always append. And then, when you're done with your loop, just remove the final character. Tons less conditionals that way too.

You can use StringBuilder's deleteCharAt(int index) with index being length() - 1

Maybe you are using the wrong tool for the Job.

This is more manual than what you are doing but it's in a way more elegant if not a bit "old school"

 StringBuffer buffer = new StringBuffer();
 Iterator iter = s.iterator();
 while (iter.hasNext()) {
      buffer.append(iter.next());
      if (iter.hasNext()) {
            buffer.append(delimiter);
      }
 }

This is almost a repeat of this StackOverflow question. What you want is StringUtils, and to call the join method.

StringUtils.join(strArr, ',');

Another solution (perhaps the most efficient)

    int[] array = {1, 2, 3};
    StringBuilder builder = new StringBuilder();

    if (array.length != 0) {
        builder.append(array[0]);
        for (int i = 1; i < array.length; i++ )
        {
            builder.append(",");
            builder.append(array[i]);
        }
    }

keep it simple and use a standard for loop:

for(int i = 0 ; i < array.length ; i ++ ){
    builder.append(array[i]);
    if( i != array.length - 1 ){
        builder.append(',');
    }
}

or just use apache commons-lang StringUtils.join()

Explicit loops always work better than implicit ones.

builder.append( "" + array[0] );
for( int i = 1; i != array.length; i += 1 ) {
   builder.append( ", " + array[i] );
}

You should wrap the whole thing in an if-statement just in case you're dealing with a zero-length array.

If you convert it to a classic index loop, yes.

Or you could just delete the last comma after it's done. Like so:

int[] array = {1, 2, 3...};
StringBuilder

builder = new StringBuilder();

for(int i : array)
{
    builder.append(i + ",");
}

if(builder.charAt((builder.length() - 1) == ','))
    builder.deleteCharAt(builder.length() - 1);

Me, I just use StringUtils.join() from commons-lang.

Here is a solution:

int[] array = {1, 2, 3...};
StringBuilder builder = new StringBuilder();
bool firstiteration=true;

for(int i : array)
{
    if(!firstiteration)
        builder.append(",");

    builder.append("" + i);
    firstiteration=false;
}

Look for the first iteration :)  

You need Class Separator.

Separator s = new Separator(", ");
for(int i : array)
{
     builder.append(s).append(i);
}

The implementation of class Separator is straight forward. It wraps a string that is returned on every call of toString() except for the first call, which returns an empty string.

Based on java.util.AbstractCollection.toString(), it exits early to avoid the delimiter.

StringBuffer buffer = new StringBuffer();
Iterator iter = s.iterator();
for (;;) {
  buffer.append(iter.next());
  if (! iter.hasNext())
    break;
  buffer.append(delimiter);
}

It's efficient and elegant, but not as self-evident as some of the other answers.

Yet another option.

StringBuilder builder = new StringBuilder();
for(int i : array)
    builder.append(',').append(i);
String text = builder.toString();
if (text.startsWith(",")) text=text.substring(1);

Many of the solutions described here are a bit over the top, IMHO, especially those that rely on external libraries. There is a nice clean, clear idiom for achieving a comma separated list that I have always used. It relies on the conditional (?) operator:

Edit: Original solution correct, but non-optimal according to comments. Trying a second time:

    int[] array = {1, 2, 3};
    StringBuilder builder = new StringBuilder();
    for (int i = 0 ;  i < array.length; i++)
           builder.append(i == 0 ? "" : ",").append(array[i]); 

There you go, in 4 lines of code including the declaration of the array and the StringBuilder.

Another approach is to have the length of the array (if available) stored in a separate variable (more efficient than re-checking the length each time). You can then compare your index to that length to determine whether or not to add the final comma.

EDIT: Another consideration is weighing the performance cost of removing a final character (which may cause a string copy) against having a conditional be checked in each iteration.

Two alternate paths here:

1: Apache Commons String Utils

2: Keep a boolean called first, set to true. In each iteration, if first is false, append your comma; after that, set first to false.

If you're only turning an array into a comma delimited array, many languages have a join function for exactly this. It turns an array into a string with a delimiter between each element.

You can use StringJoiner.

int[] array = { 1, 2, 3 };
StringJoiner stringJoiner = new StringJoiner(",");

for (int i : array) {
    stringJoiner.add(String.valueOf(i));
}

System.out.println(stringJoiner);