How to search in a List of Java object

Question

I have a List of object and the list is very big. The object is

class Sample {
    String value1;
    String value2;
    String value3;
    String value4;
          


        

Answer 1

If you always search based on value3, you could store the objects in a Map:

Map> map = new HashMap <>();

You can then populate the map with key = value3 and value = list of Sample objects with that same value3 property.

You can then query the map:

List allSamplesWhereValue3IsDog = map.get("Dog");

Note: if no 2 Sample instances can have the same value3, you can simply use a Map.