What are the different ways of performing sorting in java

Question

This question was asked in an interview . Except Collections.sort() what are the other methods .

Answer 1

Arrays.sort(..), or implement sorting yourself.

Answer 2

1. Insertion Sort is used for small size arrays.
2. Dual Pivot Quick Sort is used for larger size arrays.
3. MergeSort is used for sorting object.

Answer 3

You can stick your data into a SortedSet (e.g. TreeSet) and pull it out again in sorted order by traversing with an iterator. This is not really a general sorting method (since it doesn't allow duplicated entries), but would work for quite a lot of data set.

Answer 4

Comparable and Comparator are the standard interfaces used by all standard Java sorting options (all except those on primitive arrays, that is).

In Java-speak, any Class that implements Comparable has a "natural order". (Technically, it must implement Comparable<? super E> where E matches itself, to have a natural order). Classes that don't have a natural order can be sorted using an external Comparator. A Comparator can also be used to implement a sort order that runs against the natural order (e.g. sort Strings in descending alphabetic order).

These principles are applied both in the SortedSet and SortedMap implementations, that sort their elements / keys automatically using either the natural order or a supplied comparator.

These same principles can also be found in the static Utility methods

• Arrays.sort(arr) and Arrays.sort(arr, comparator) for Arrays
• Collections.sort(list) and Collections.sort(list, comparator) for Lists

that can be used to sort arrays and lists, respectively, each of which don't support sorting themselves.

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The Guava Library takes this a bit further by providing the abstract Ordering class as base implementation of Comparator which already contains standard methods like providing a reverse view of itself and many convenience methods for sorting and retrieving based on this Ordering.

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Reference

A good article about Object Ordering can be found in the Sun Java Tutorial's Collection Trail.

Answer 5

1. SortedSet or SortedMap, provided the keys are unique.
2. PriorityQueue.
3. Arrays.sort().
4. Own code.
5. A JDBC query with an ORDER BY clause.
6. An LDAP search against an indexed attribute.

I'm sure there are more.