Create formatted string from ArrayList

Question

Consider following code:

    ArrayList aList = new ArrayList();
    aList.add(2134);
    aList.add(3423);
    aList.add(4234);
         


        

Answer 1

for(int aValue : aList) {
    if (aValue != aList.Count - 1)
    {
          tmpString += aValue + ",";
    }
    else
    {
          tmpString += aValue + ")";
    }
}

Perhaps?

Answer 2

You could use Commons Lang:

String tmpString = "(" + StringUtils.join(aList, ",") + ")";

Alternatively, if you can't use external libraries:

StringBuilder builder = new StringBuilder("(");
for (int aValue : aList) builder.append(aValue).append(",");
if (aList.size() > 0) builder.deleteCharAt(builder.length() - 1);
builder.append(")");
String tmpString = builder.toString();

Answer 3

If you used an Iterator you could test hasNext() inside your loop to determine whether you needed to append a comma.

StringBuilder builder = new StringBuilder();
builder.append("(");

for(Iterator<Integer> i=aList.iterator(); i.hasNext();)
{
  builder.append(i.next().toString());
  if (i.hasNext()) builder.append(",");
}

builder.append(")");

Answer 4

You will have to replace the last comma with a ')'. But use a StringBuilder instead of adding strings together.

Answer 5

How about this from google-guava

String joinedStr = Joiner.on(",").join(aList);

System.out.println("("+JjoinedStr+")");

Answer 6

Building off Mateusz's Java 8 example, there's an example in the StringJoiner JavaDoc that nearly does what OP wants. Slightly tweaked it would look like this:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4);

String commaSeparatedNumbers = numbers.stream()
     .map(i -> i.toString())
     .collect( Collectors.joining(",","(",")") );