A comparator, with additional methods to support common operations. This is an “enriched” version of Comparator. The common ways to get an instance of Ordering are :
- Subclass it and implement compare(T, T) instead of implementing Comparator directly.
- Pass a pre-existing Comparator instance to from(Comparator).
- Use the natural ordering, natural().
Declaration : The declaration for com.google.common.collect.Ordering<T> class is :
@GwtCompatible
public abstract class Ordering<T>
extends Object
implements Comparator<T>
Below given are some methods provided by Guava’s Ordering Class :
Ordering() : This is a constructor of Ordering Class of Guava. It constructs a new instance of this class (only invokable by the subclass constructor, typically implicit). Some other methods provided by this Class are :
Exceptions :
- explicit(List valuesInOrder) : NullPointerException if any of the provided values is null, IllegalArgumentException if valuesInOrder contains any duplicate values.
- explicit(T leastValue, T… remainingValuesInOrder) : NullPointerException if any of the provided values is null, IllegalArgumentException if any duplicate values.
- min(Iterator iterator) : NoSuchElementException if iterator is empty, ClassCastException if the parameters are not mutually comparable under this ordering.
- min(Iterable iterable) : NoSuchElementException if iterable is empty, ClassCastException if the parameters are not mutually comparable under this ordering.
- min(E a, E b) : ClassCastException if the parameters are not mutually comparable under this ordering.
- min(E a, E b, E c, E… rest) : ClassCastException if the parameters are not mutually comparable under this ordering.
- max(Iterator iterator) : NoSuchElementException if iterator is empty, ClassCastException if the parameters are not mutually comparable under this ordering.
- max(Iterable iterable) : NoSuchElementException if iterable is empty, ClassCastException if the parameters are not mutually comparable under this ordering.
- max(E a, E b) : ClassCastException if the parameters are not mutually comparable under this ordering.
- max(E a, E b, E c, E… rest) : ClassCastException if the parameters are not mutually comparable under this ordering.
- leastOf(Iterable iterable, int k): IllegalArgumentException if k is negative.
- leastOf(Iterator elements, int k) : IllegalArgumentException if k is negative.
- greatestOf(Iterable iterable, int k): IllegalArgumentException if k is negative.
- greatestOf(Iterator elements, int k) : IllegalArgumentException if k is negative.
- immutableSortedCopy : NullPointerException if any of elements (or elements itself) is null.
Some other methods provided by this class are :
Example 1 :
// Java code to show implementation of// Ordering classimport java.util.*; import com.google.common.collect.Ordering; class GFG { // Driver code public static void main(String args[]) { // Creating a list of Integers List<Integer> myList = new ArrayList<Integer>(); myList.add(new Integer(12)); myList.add(new Integer(3)); myList.add(new Integer(78)); myList.add(new Integer(50)); myList.add(new Integer(6)); myList.add(new Integer(70)); myList.add(new Integer(18)); myList.add(new Integer(9)); myList.add(new Integer(10)); // Displaying natural order of numbers Ordering ordering = Ordering.natural(); System.out.println("Input List : " + myList); // Displaying the sorted list Collections.sort(myList, ordering); System.out.println("Sorted List : " + myList); }} |
Output :
Input List : [12, 3, 78, 50, 6, 70, 18, 9, 10] Sorted List : [3, 6, 9, 10, 12, 18, 50, 70, 78]
Below given are some other methods provided by Ordering Class of Guava :
Example 2 :
// Java code to show implementation of// Ordering classimport java.util.*; import com.google.common.collect.Ordering; class GFG { // Driver code public static void main(String args[]) { // Creating a list of Integers List<Integer> myList = new ArrayList<Integer>(); myList.add(new Integer(12)); myList.add(new Integer(3)); myList.add(new Integer(78)); myList.add(new Integer(50)); myList.add(new Integer(6)); myList.add(new Integer(70)); myList.add(new Integer(18)); myList.add(new Integer(9)); myList.add(new Integer(10)); // Displaying natural order of numbers Ordering ordering = Ordering.natural(); System.out.println("Minimum element is : " + ordering.min(myList)); }} |
Output :
Minimum element is : 3
Example 3 :
// Java code to show implementation of// Ordering classimport java.util.*; import com.google.common.collect.Ordering; class GFG { // Driver code public static void main(String args[]) { // Creating a list of Integers List<Integer> myList = new ArrayList<Integer>(); myList.add(new Integer(12)); myList.add(new Integer(3)); myList.add(new Integer(78)); myList.add(new Integer(50)); myList.add(new Integer(6)); myList.add(new Integer(70)); myList.add(new Integer(18)); myList.add(new Integer(9)); myList.add(new Integer(10)); // Displaying natural order of numbers Ordering ordering = Ordering.natural(); System.out.println("Maximum element is : " + ordering.max(myList)); }} |
Output :
Maximum element is : 78
Example 4 :
// Java code to show implementation of// Ordering classimport java.util.*; import com.google.common.collect.Ordering; class GFG { // Driver code public static void main(String args[]) { // Creating a list of Integers List<Integer> myList = new ArrayList<Integer>(); myList.add(new Integer(12)); myList.add(new Integer(3)); myList.add(new Integer(78)); myList.add(new Integer(50)); myList.add(new Integer(6)); myList.add(new Integer(70)); myList.add(new Integer(18)); myList.add(new Integer(9)); myList.add(new Integer(10)); // Displaying natural order of numbers Ordering ordering = Ordering.natural(); // To get reverse of original list Collections.sort(myList, ordering.reverse()); // Displaying the reversed elements System.out.println(myList); }} |
Output :
[78, 70, 50, 18, 12, 10, 9, 6, 3]
Reference : Google Guava
