Sorted collection in Java

java sorting collections
rohan picture rohan · Jan 6, 2009 · Viewed 191.1k times · Source

I'm a beginner in Java. Please suggest which collection(s) can/should be used for maintaining a sorted list in Java. I have tried Map and Set, but they weren't what I was looking for.

Answer

Martin Probst picture Martin Probst · Feb 24, 2010

This comes very late, but there is a class in the JDK just for the purpose of having a sorted list. It is named (somewhat out of order with the other Sorted* interfaces) "java.util.PriorityQueue". It can sort either Comparable<?>s or using a Comparator.

The difference with a List sorted using Collections.sort(...) is that this will maintain a partial order at all times, with O(log(n)) insertion performance, by using a heap data structure, whereas inserting in a sorted ArrayList will be O(n) (i.e., using binary search and move).

However, unlike a List, PriorityQueue does not support indexed access (get(5)), the only way to access items in a heap is to take them out, one at a time (thus the name PriorityQueue).

Related questions

Sort a Map<Key, Value> by values

I am relatively new to Java, and often find that I need to sort a Map<Key, Value> on the values. Since the values are not unique, I find myself converting the keySet into an array, and sorting …

Read More
How to sort an ArrayList?

I have a List of doubles in java and I want to sort ArrayList in descending order. Input ArrayList is as below: List<Double> testList = new ArrayList(); testList.add(0.5); testList.add(0.2); testList.add(0.9); testList.add(0.1); testList.add(0.1); testList.…

Read More
How to sort an ArrayList in Java

I have a class named Fruit. I am creating a list of this class and adding each fruit in the list. I want to sort this list based on the order of fruit name. public class Fruit{ private String fruitName; …

Read More