The best resource is straight from the official API: The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared … Read more
If you’re comparing HashMap with ArrayList, I presume you’re doing some sort of searching/indexing of the ArrayList, such as binary search or custom hash table…? Because a .get(key) thru 6 million entries would be infeasible using a linear search. Using that assumption, I’ve done some empirical tests and come up with the conclusion that “You … Read more
Collections.sort(teamsName.subList(1, teamsName.size())); The code above will reflect the actual sublist of your original list sorted.
My experiment shows that HashSet is faster than an ArrayList starting at collections of 3 elements inclusively. A complete results table | Boost | Collection Size | | 2x | 3 elements | | 3x | 10 elements | | 6x | 50 elements | | 12x | 200 elements | <= proportion 532-12 vs … Read more
On the records property add: @XmlElementWrapper(name=”records”) @XmlElement(name=”data”) For more information on JAXB and collection properties see: JAXB & Collection Properties
This is the solution for my old question: I implemented my own ContextResolver in order to enable the DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY feature. package org.lig.hadas.services.mapper; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; import javax.ws.rs.ext.ContextResolver; import javax.ws.rs.ext.Provider; import org.codehaus.jackson.map.DeserializationConfig; import org.codehaus.jackson.map.ObjectMapper; @Produces(MediaType.APPLICATION_JSON) @Provider public class ObjectMapperProvider implements ContextResolver<ObjectMapper> { ObjectMapper mapper; public ObjectMapperProvider(){ mapper = new ObjectMapper(); mapper.configure(DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true); } @Override public … Read more
It depends on how efficient you need things to be. Simply iterating over the list looking for the element which satisfies a certain condition is O(n), but so is ArrayList.Contains if you could implement the Equals method. If you’re not doing this in loops or inner loops this approach is probably just fine. If you … Read more
You can make it like : List<Object> sections = new ArrayList <Object>(); (Recommended) Another possible solution would be to make a custom model class with two parameters one Integer and other String. Then using an ArrayList of that object.
To insert value into ArrayList at particular index, use: public void add(int index, E element) This method will shift the subsequent elements of the list. but you can not guarantee the List will remain sorted as the new Object you insert may sit on the wrong position according to the sorting order. To replace the … Read more
Since this is actually not a list of strings, the easiest way is to loop over it and convert each item into a new list of strings yourself: List<String> strings = list.stream() .map(object -> Objects.toString(object, null)) .toList(); Or when you’re not on Java 16 yet: List<String> strings = list.stream() .map(object -> Objects.toString(object, null)) .collect(Collectors.toList()); Or … Read more