Java ArrayList merge without duplicates based on a value -

i have class called sample, class has property arraylist<area>, , area contains arraylist<elements>

public class sample {     private arraylist<area> sampleareas;     public arraylist<element> getmergeddata()     {         ...     }     ... }  public class area {     private arraylist<element> areaelements     ... }  public class element {     private string name;     private float value;     ... } 

i need getmergeddata() sample class merges every arraylist<elements> each of it's area, keeping element bigger value.

ex:

area 1: ("element k" => 1.0, "element c" => 0.5, "element as" => 15.0)

area 2: ("element k" => 10.1, "element c" => 5.5, "element as" => 2.9, "element o" => 1.5)

area 3: ("element c" => 2.8, "element as" => 0.5, "element o" => 5.8)

area 4: ("element k" => 3.25, "element as" => 2.5, "element o" => 0.1)

so, method must return this: ("element k" => 10.1, "element c" => 5.5, "element as" => 15.0, "element o" => 5.8"

i can't figure out how can in fashion way.

if lists' elements same order, e.g. k element first, c element second, etc., element-by-element comparison. otherwise, can sort them on element names , element-by-element comparison (this nlog(n) if use sort algorithm), or else put in hashmap element name key , value value.

hashmap map = new hashmap(); for(int = 0; < list1.size(); i++) {     element e = list1.get(i);     map.put(e.name, e.value); } for(int = 0; < list2.size(); i++) {     element e = list2.get(i);     if(map.get(e.name) < e.value)         map.put(e.name, e.value); }