Question

I need to put comma separated values into ourOutput (for future output). So, what I need is to add commas and remove last unnecessary comma or check if comma should be placed.

I came to two following solutions:

1st approach:

ourOutput  = ''<<'';
for (int i = 0; i< 10, i++) {
  if (/*some condition goes here*/) {
    if (ourOutput.size() == 0) {
      ourOutput << ', '
    } 
    ourOutput << i;
  }
}

pros: don’t change resulting string
cons: check on each iteration;

2nd approach:

ourOutput  = ''<<'';
for (int i = 0; i< 10, i++) {
  if (/*some condition goes here*/) {
    ourOutput << i << ', ';
  }
}
if (ourOutput.size() != 0) {
  ourOutput.setLength(ourOutput.length() - 2);
} 

pros: don’t check each time
cons: modifying resulting string.

Please advise, which one to use or maybe there is some better way to do that?

p.s. code written in groovy, feel free to replace ”<<” with new StringBuilder() and << with .append() so it became java-compilable.

Answer 1

There’s an excellent library to aid you with this, Commons Lang StringUtils

StringUtils.join(C, ",");

where C can be either a Collection, Array, or Iterator.