Comparator vs Comparable in Java
Comparators and comparable in Java are two interfaces which is used to implement sorting in Java. It’s often required to sort objects stored in any collection classes like ArrayList, HashSet or in Array and that time we need to use either compare() or compareTo() method defined in java.util.Comparatorand java.lang.Comparable.
1) Comparator in Java is defined in java.util package while Comparable interface in Java is defined injava.lang package, which very much says that Comparator should be used as an utility to sort objects whichComparable should be provided by default.
Comparators and comparable in Java are two interfaces which is used to implement sorting in Java. It’s often required to sort objects stored in any collection classes like ArrayList, HashSet or in Array and that time we need to use either compare() or compareTo() method defined in java.util.Comparatorand java.lang.Comparable.
1) Comparator in Java is defined in java.util package while Comparable interface in Java is defined injava.lang package, which very much says that Comparator should be used as an utility to sort objects whichComparable should be provided by default.
4) Comparable in Java is used to implement natural ordering of object. In Java API String, Date and wrapper classes implements Comparable interface.Its always good practice to override compareTo() for value objects.
5) If any class implement Comparable interface in Java then collection of that object either List or Array can be sorted automatically by using Collections.sort() or Arrays.sort() method and object will be sorted based on there natural order defined by CompareTo method.
6)Objects which implement Comparable in Java can be used as keys in a SortedMap like TreeMap or elements in aSortedSet for example TreeSet, without specifying any Comparator.
When to use Comparator and Comparable in Java
1) If there is a natural or default way of sorting Object already exist during development of Class than use Comparable. On the other hand if an Object can be sorted on multiple ways and client is specifying on which parameter sorting should take place than use Comparator interface.
2) Some time you write code to sort object of a class for which you are not the original author, or you don't have access to code. In these cases you can not implement Comparable and Comparator is only way to sort those objects.
3) Beware with the fact that How those object will behave if stored in SorteSet or SortedMap like TreeSet and TreeMap. If an object doesn't implement Comparable than while putting them into SortedMap, always provided correspondingComparator which can provide sorting logic.
4) Order of comparison is very important while implementing Comparable or Comparator interface.
