What are the different ways to do sorting in java

Question

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

Answer 1

Sorting interfaces

Comparable<T> and Comparator<T> are the standard interfaces used by all standard Java sorting options (all except those related to primitive arrays).

In Java-talk, any class that implements Comparable has a "natural order". (Technically, he should implement Comparable<? super E> , where E matches itself, to have a natural order). Classes that do not have a natural order can be sorted using an external comparator. The comparator can also be used to implement a sort order that runs against the natural order (for example, sorting strings in descending alphabetical order).

These principles apply to both SortedSet<E> and SortedMap<K,V> , which sort their elements / keys automatically, using either the natural order or the supplied comparator.

The same principles can also be found in the static methods of the Utility.

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

which can be used to sort arrays and lists, respectively, each of which does not support sorting.

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guavas

The Guava library takes this a bit further by providing abstract Ordering as a basic Comparator implementation that already contains standard methods, such as providing a reverse view of yourself and many convenient methods for sorting and retrieving based on this Ordering .

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Link

A good article on Ordering Objects can be found in the Sun Java Trail Collection Tutorial .

Answer 2

• SortedSet or SortedMap if the keys are unique.
• PriorityQueue.
• Arrays.sort ().
• Native code.
• JDBC query with ORDER BY clause.
• LDAP search with indexed attribute.

I am sure there are more of them.

Answer 3

• The Sort insert is used for small arrays.
• Double Pivot Quick Sort is used for larger arrays.
• MergeSort is used to sort an object.

Answer 4

Arrays.sort(..) or do the sorting yourself.

Answer 5

You can paste your data into a SortedSet (e.g. TreeSet ) and pull it out again in sorted order by going through an iterator. This is not a general sorting method (since it does not allow duplicate entries), but will work for a fairly large dataset.