Create formatted string from ArrayList

Question

Consider following code:

    ArrayList<Integer> aList = new ArrayList<Integer>();
    aList.add(2134);
    aList.add(3423);
    aList.add(4234);
    aList.add(343);

    String tmpString = "(";

    for(int aValue : aList) {
        tmpString += aValue + ",";
    }
    tmpString = (String) tmpString.subSequence(0, tmpString.length()-1) + ")";

    System.out.println(tmpString);

My result here is (2134,3423,4234,343) as expected..

I do replace the last comma with the ending ) to get expected result. Is there a better way of doing this in general?

Rob Hruska · Accepted Answer · 2011-02-04 21:39:53Z

17

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();

edited Feb 4, 2011 at 21:39

answered Jan 12, 2011 at 16:35

Rob Hruska

121k32 gold badges170 silver badges193 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Dominik Sandjaja Over a year ago

I prefer the Commons Lang approach as well, especially as I have it as a dependency in all projects anyway.

Rob Hruska Over a year ago

I usually end up using it for one reason or another as well. No reason to reinvent the wheel unless you have specific constraints restricting you from using external libraries. Some of the Apache Commons libraries have their drawbacks when it comes to collections and generics, but StringUtils is pretty straightforward.

StefanE Over a year ago

Very neat solution! I knew there must be a way to do this in a one liner.. And the StringUtils lib is almost standard to include anyway.

MrMeszaros · Accepted Answer · 2015-01-15 15:49:18Z

8

Since Java 8 you can also do:

ArrayList<Integer> intList = new ArrayList<Integer>();
intList.add(2134);
intList.add(3423);
intList.add(4234);
intList.add(343);

String prefix = "(";
String infix = ", ";
String postfix = ")";

StringJoiner joiner = new StringJoiner(infix, prefix, postfix);
for (Integer i : intList)
    joiner.add(i.toString());

System.out.println(joiner.toString());

answered Jan 15, 2015 at 15:49

MrMeszaros

70311 silver badges21 bronze badges

Comments

jzd · Accepted Answer · 2011-01-12 16:36:29Z

2

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

answered Jan 12, 2011 at 16:36

jzd

23.6k9 gold badges58 silver badges76 bronze badges

Comments

Aravind Yarram · Accepted Answer · 2011-01-12 19:46:01Z

2

How about this from google-guava

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

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

edited Jan 12, 2011 at 19:46

answered Jan 12, 2011 at 16:43

Aravind Yarram

80.5k49 gold badges239 silver badges335 bronze badges

Comments

DanM · Accepted Answer · 2016-10-11 18:24:57Z

1

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(",","(",")") );

answered Oct 11, 2016 at 18:24

DanM

1211 silver badge6 bronze badges

Comments

Qwerky · Accepted Answer · 2011-01-12 16:53:30Z

0

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(")");

edited Jan 12, 2011 at 16:53

answered Jan 12, 2011 at 16:46

Qwerky

18.5k6 gold badges48 silver badges84 bronze badges

Comments

m.edmondson · Accepted Answer · 2011-01-12 16:34:19Z

-1

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

Perhaps?

answered Jan 12, 2011 at 16:34

m.edmondson

30.9k29 gold badges129 silver badges212 bronze badges

Collectives™ on Stack Overflow

Create formatted string from ArrayList

7 Answers 7

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related