Removing last comma or other delimiter when printing list to string

Question

Let's assume that I have a datastructure with n elements (0, 1, ... , n-1).

And assume these elements have some property I want to print (assume an int). And I want to print the datastructure on one line, with a delimiter (comma, space). So, the result would be something like this

13, 14, 15, 16, 17

What is the best way to add the comma and space (in Java)?

These are approaches I've taken:

1. If the datastructure is Iterable, iterate from 0 to n-2 and append the delimiter to each of those, then print the last element.

2. Loop through all elements and append everything to empty String (or Stringbuilder), then at the very end remove the last deliminator (hardcoded).

I feel like there's something better.

Edit: The question is unique. The 'possible duplicate' involves only printing, not messing with delimiters.

Edit2: Attempts as requested

// 1st approach
public void printStuff(ArrayList<Integer> input) {
    for (int i=0; i<input.size()-1; i++) {
        System.out.print(input.get(i) + ", ");
    }
    System.out.println(input.get(input.size()-1);
}

Another attempt

// 2nd approach
public void printStuff(ArrayList<Integer> input) {
    StringBuilder sb = new StringBuilder();
    for (int i=0; i<input.size(); i++) {
        sb.append(input.get(i)+", ");
    }
    sb.substring(0, input.size()-2);
    System.out.println(sb.toString());
}

Answer 1

Java 8's streaming APIs finally provide an elegant, native, way of doing this without resorting to ugly if-else structures or using third parties.

Assuming you have a list of MyClass objects, and assuming MyClass has a getPropery() access method that returns an int, you could do something like this:

List<MyClass> list = ...;
String concatination = list.stream()
                           .map(p -> String.valueOf(p.getProperty()))
                           .collect(Collectors.joining(", "));

Answer 2

Using an iterator I would check whether there are any items left. If so, add a separator:

if (i.hasNext()) s.append(", ");

Answer 3

Use some Java 8 Stream magic:

List<Integer> list = Arrays.asList(1, 2, 3) //just so we have a list to work on
String result = list.stream()
        .map(it -> it.toString())
        .collect(Collectors.joining(", "))

Answer 4

You could use a framework, like this:

https://google-collections.googlecode.com/svn/trunk/javadoc/com/google/common/base/Joiner.html

Joiner.on(",").join(list)

Answer 5

You could remove the first element, add it to your String and add , <string> to it:

List<String> lst = new ArrayList<String>();

// add elements

StringBuilder buffer = new StringBuilder();
buffer.append(lst.remove(0));

for(String s : lst) {
    buffer.append(", ").append(s);
}