Java Essentials - Comparator to sort lists

In this video we are discussing comparator to short lists

We know that comparator is one interface and this interface is having mainly two methods

are there. One is the equals and the one is the compared

So compared and equals two methods are there. So to use this comparator obviously I must be defining one class which will implement this

comparator interface and then we can define those methods and you can use them

So let us go for further discussion on this. So what is comparator

The comparator is an interface and that is used to compare two objects of a class

And in this interface there are two methods are there. One is the compared and the one is the equals

So we need to create a class that can implement this comparator interface

Then only we can have these methods getting called and getting executed

it in the collection classes like our add a list or say in case of link list that is a method known as the short method so there is a short method is there in it is available in case of both add a list and in case of link list there is a method known as the short method So there is a short method is there It is available in case of both add a list and in case of link list

Using this we can short lists. So this short method needs this comparator to compare objects

for the shorting operation. So now let us go for one practical demonstration for your better

understanding and there will be discussing all this concept using one Java sample code. So here is the demonstration

for you we are defining one class that is a string compared which implements the

interface comparator this comparative interface is defined under the package Java dot util and this particular comparative interface is is having only one

unimplemented method that is a compared so this the compare is the one

unimplemented method in this interface that is a comparator and in this

particular compare we are having two input arguments that is a compare is the T O1 and T O2 that is a type object one and type object two

Let us go for detail description here You can find that compares it compares it two arguments for the order return a negative integer zero or a positive

integer as a first argument is less than equal to or greater than the second

argument and that is the purpose of this compare so compare is the method which we

have implemented here which returns return STR 1 dot compared to STR 2. Here we have passed this string STR 1 and STR 2 as two objects to this

compared method. So string compared is nothing but our user defined class which is

implementing the interface comparator which is defined under the package Java. Util. So here we're having another class that is our comparator demo. Under the

main function we have defined one add a list object that is a city list and we

have added multiple string objects to this city list. at a object and we have printed this current content of the city list so let us go

for the execution you can find that we have printed all the current content of the city list and when the cities are unshorted so Delhi Kolkata Hyderabad Chennai and Lucknow they have got printed now short the ad list in the alphabetical order using the method short and as an input

argument we are passing the string comparator class object which has already

implemented the comparative interface and also implemented the method that is a

compared so city list dot shot new string compared so here we are calling the the string compared class constructor that

is with that new we are actually passing the string compared compared class

object as input argument to this short method so now if we go on printing

this add list content we are getting that this are a list content have got

shorted in the alphabetical order so now the order has become Chennai Delhi

Hyderabad Kolkata and Lochnu and you can find that they have got sorted in the alphabetical order

in the ascending order. In this way in this particular demonstration we have shown

you that how to use the comparative interface in our Java code. Thanks for watching

this video