Question

Is there a better way to find closest object with lesser marker?

class Prop implements Comparable {
  BigDecimal marker
  String value

  int compareTo(other) {
    return marker <=> other.marker
  }

}

def props = [new Prop(marker: 0G, value: "1st"),
new Prop(marker: 20G, value: "2nd"),
new Prop(marker: 30G, value: "3rd"),
new Prop(marker: 40G, value: "4th"),
new Prop(marker: 50G, value: "5th"),
new Prop(marker: 100G, value: "6th"),
new Prop(marker: 1000G, value: "7th")]

def whereAmI = 44G

def here = props.findAll{it.marker <= whereAmI}.max()

Answer 1

Edit: Updated to return the correct object type, and nulls.

Assuming that order isn’t guaranteed, you could use the inject method:

// Inject null, so if nothing is lower than max, this returns null
def here = props.inject(null){ max, it ->
    (it.marker <= whereAmI && (!max || it > max)) ? it : max
}

If the list is always sorted, then simply use this:

// Inject null, so if nothing is lower than max, this returns null
def here = props.inject(null){ max, it ->
    (it.marker <= whereAmI) ? it : max
}

The benefit here is you only loop over the set once, and you don’t create an additional interim List of lesser values.

Now, depending on your list size, the argument may be that your original example is a lot easier to read, and a lot clearer. Clarity in code can trump performance.

(Note: inject is Groovy’s version of reduce or fold.)