How to Create TreeMap Objects using Comparable Interface in Java?
Comparable interface is found in java.lang package which is used to order the objects of a user-defined class on the basis of a single attribute only. This interface contains a single method compareTo(Object). It is used to compare the current object with the specified objects and can be used o sort user-defined classes, wrapper class, and string objects.
compareTo(Object o) ;
Parameter: The specified object with which the current object is being compared.
Return Type: Integer value
- Positive integer — If the current object is greater than the specified object.
- Negative integer — If the current object is lesser than the specified object.
- Zero — If the current object is equal to the specified object.
Use of Comparable Interface in Java
TreeMap in Java, elements are stored as key-value pairs which are sorted on the basis of the key. When the Key is of String class or Wrapper Classes, it implements the Comparable interface by default and stores the elements in sorted order. However, if somebody wants to make the desired key of a particular user-defined type i.e user-defined class, we need to implement the Comparable interface to order the objects in a particular order on the basis of an attribute.
Implementation: Without using the comparable interface.
The above code throws exceptions as the comparable interface has not been implemented and hence it cannot order the map elements on the basis of a key in proper order. So, in order to handle the exception
Implementation: With using the comparable interface.
1 Pathak First 2 Anshu Second