Java collection/map apply method equivalent?

Question

I would like to apply a function to a Java collection, in this particular case a map. Is there a nice way to do this? I have a map and would like to just run trim() on all t

Answer 1

With Java 8's lambdas, this is a one liner:

map.replaceAll((k, v) -> v.trim());

For the sake of history, here's a version without lambdas:

public void trimValues(Map map) {
  for (Map.Entry e : map.entrySet()) {
    String val = e.getValue();
    if (val != null)
      e.setValue(val.trim());
  }
}

Or, more generally:

interface Function {
  T operate(T val);
}

public static  void replaceValues(Map map, Function f)
{
  for (Map.Entry e : map.entrySet())
    e.setValue(f.operate(e.getValue()));
}

Util.replaceValues(myMap, new Function() {
  public String operate(String val)
  {
    return (val == null) ? null : val.trim();
  }
});