dubey-theHarcourtians dubey-theHarcourtians - 1 year ago 60
Java Question

Performing the fastest search - which collection should i use?

I know:

  • If you need fast access to elements using index, ArrayList should be choice.

  • If you need fast access to elements using a key, use HashMap.

  • If you need fast add and removal of elements, use LinkedList (but it has a very poor seeking performance).

In order to perform the fastest search, on the basis of data stored in a collection object, which collection should I use?

Below is my code:

public void fillAndSearch(Collection<Student> collection) {
for (int i=0; i<=10; i++) {
Student student = new Student("name" + i, "id" + i);
//here We have to perform searching for "name7" or "id5",
//then which implementation of collection will be fastest?

class Student {
String name;
String id;

Student(String name, String id) {
this.name = name;
this.id = id;

Answer Source

The thing which is often skipped when comparing ArrayList and LinkedList is cache and memory management optimisations. ArrayList is effectively just an array which means that it is stored in a continuous space in the memory. This allows the Operating System to use optimisations such as "when a byte in memory was accessed, most likely the next byte will be accessed soon". Because of this, ArrayList is faster than LinkedList in all but one case: when inserting/deleting the element at the beginning of the list (because all elements in the array have to be shifted). Adding/deleting at the end or in the middle, iterating over, accessing the element are all faster in case of ArrayList.

If you need to search for student with given name and id, it sounds to me like a map with composite key - Map<Student, StudentData>. I would recommend to use HashMap implementation, unless you need to be able to both search the collection and retrieve all elements sorted by key in which case TreeMap may be a better idea. Although remember that HashMap has O(1) access time, while TreeMap has O(logn) access time.

I am not quite sure what you are trying to achieve - why to search this collection at all? What do you want to find in there?

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