What is the difference between comparator and comparable?

The same thing

Both are used to compare two objects “ The order ” The interface of

You can use Collections.sort() Method to sort the collection of objects

Difference

Comparable be located java.lang It's a bag , and Comparator At java.util It's a bag

Comparable It's a sort of method implementation defined within a collection ,Comparator It's a sort implemented outside the collection

summary

Use Comparable Interface to compare objects , You can make this type （ Set to A） Realization Comparable Interface , and

have access to Collections.sort() Method A Type of List Sort , And then you can go through a1.comparaTo(a2) Let's compare two

object ;

When using Comparator Interface to compare objects , Just create an implementation Comparator Comparator of interface （ set up

by AComparator）, And pass it on Collections.sort() The method can be used to A Type of List Sort , You can also adjust

Use a comparator AComparator.compare(a1, a2) To compare two objects .

It can be said that one is to complete the comparison by oneself , One is the difference between the implementation of external programs .

use Comparator It's the strategy model （strategy design pattern）, It's not changing the object itself , And with a strategy object

（strategy object） To change its behavior .

such as ： You want to sort integers in absolute size ,Integer It doesn't meet the requirements , You don't need to modify Integer class （ actual

You can't do that ） To change its ordering behavior , At this time, just （ There is only a ） Using an implementation Comparator Interface

Object to control its sorting .

Two ways , Each has its own characteristics ： Use Comparable When comparing ways , We write the rules of comparison into the type of comparison , Its

Characterized by high cohesion . But if one day this rule needs to be changed , So we have to modify the source code of this type . If you use

Comparator Way comparison , So we don't need to modify the comparison class , It is easy to maintain , But you need to customize a comparator ,

Subsequent changes to the comparison rules , Just change the code in the comparator .