What does keySet().toArray(new Double[0]) do?

Question

What does the following return do? And how can I use that value:

private Map<Double, String> theLabels = new HashMap<Double, String>();

public Double[] getTheLabels() {
  return theLabels.keySet().toArray(new Double[0]);
  }

Is this correct?

Double[] aD = theClassInQuestion.getTheLabels();

Thanks in advance.

HJW

Answer 1

It is correct, however, unless the theLabels is empty, the reallocation of the array is forced. Here is an alternative:

public Double[] getTheLabels() {
    return theLabels.keySet().toArray(new Double[theLabels.size()]);
}