Comparable and Comparator

comparable&   Comparator are    used to implement sorting in the collection, just comparable the sort that is implemented within the collection, Comparator is the sort that is implemented outside the collection, so, if you want to implement the sort, A method to define the comparator interface outside the collection compare () or to implement the comparable interface within the collection CompareTo (). 

comparable is an interface that the object itself already supports for the comparison to be implemented (such as String    Integer can complete the comparison of the size of the operation)   
    
   and Comparator is a dedicated comparator, when the object does not support the comparison or the self comparison function does not meet your requirements, you can write a comparer to complete the size of the comparison between the two objects.