ArrayList In CollectionFramWork Day 60 By Kishan

Added: 2026-05-11

[00:00:33]all right can you hear me can you see the screen can you please respond in the chat video guys all right so let us start our session here today guys so guys before starting our sessions as always so let us try to have a very very small and a quick recap of the concepts which we had covered in our yesterdays class right yes so guys yesterday we have started discussing about collection framework collection framework and I told you what is actually collection framework like we have discussed why we are supposed to go to collections why like why already we are having arrays like why we are supposed to go to collections what is the difference between array and collections performance wise which is recommended memory wise which is recommended what collections will accept collections will accept only objects collection classes will accept only objects and uh performance wise what will be recommended memory wise what will be recommended after that I told you there are two root interfaces are there in collections what are those collection interface and map interface guys you need to respond please help me out please help me out how many root interfaces are there how many root interfaces are there there are two root interfaces are there okay two root interfaces are there what are those collection interface and map interface map interface in collection interface there are three child interfaces like list set and a queue in list we are having three implementation classes are there in list arraylist linked list vector and in set we are having three and in queue we are having two and in map we are having four implementation classes all these particular classes I will just discussed that's it like we did not go with in detail or else in-depth explanation now after that actually we have seen we have seen like what is like how elements will be present in list how elements will be stored in list set queue map just a basic introduction guys just a basic introduction and after that we had seen how to retrieve the data from collection classes also like I told you we can retrieve the data by using for Loop for each Loop iterator interfaces listed interfaces enumeration interface all this way we can retry the data I told you now guys today we are going to start discussing about arraylist okay guys we'll be trying to start discussing about arraylist first just let me try to create a class okay new class Class A like this okay right just a second right class classic okay now guys today we are going to discuss about arraylist okay only arraylist only addressed if time permits we will try to see or else no problem no problem guys I am saying you actually remember in IO streams when we discussed about iOS streams concept I told you guys please understand byte streams if you understand byte streams correctly all other streams are very very easy I told you and you have practiced that byte streams program and I believe you have like you understood Iowa streams very easily later on in the same manner I am speaking about collection classes also okay please understand one program correctly all other programs are same exactly same right now first I'm trying to take an arraylist okay just let me try to take a method for it method one method one now just system.out.println system.out.printlab here I am writing implementing arraylist I am trying to implement errorist means I want to write a program on errorist guys okay now now guys what I told you all these are just a second yes what I told you all these are classes I told you am right or wrong a realist is a class linked list is a class Vector is a class hashed at linked asset linked list all these are classes now what I want you to do is guys can you create an object for an arraylist can you create an object for error list can you please give me the code please give me the code how to create an object for arraylist just give me the code that's it I don't want anything else how to create an object for a list nikhil very good upendra that is correct Rabia perfect yes yes and uh who else give me yeah Mukesh Suma Krishna exactly alpesh rathod sushil guys exactly exactly and I thought I wanted you to create okay right right so guys please observe here please observe generally guys if you want to create an object the first keyword which we are going to use what is the first keyword new exactly first go with new okay which object you want to create error list so what we need to do we need to initialize with that Constructor okay arraylist arraylist like this arraylist like this I have initialized the error list now just let me try to have a reference AAL just a reference eal belongs to arraylist like this okay that's it not more than that you know this you know this way guys do you know this I just create an object that's it not more than that I just created an object now did you remember I told you all these all these collection classes are present in which package foreign classes are present in which package Java dot util package so obviously we need to import that arraylist I mean of course error list is a class which is present in util package so I just imported now guys I have created an arraylist now what I want to do you know I want to pass some elements into my error list I want to send some elements into my error list if I want to pass some elements I need to use a method known as guys in collection interface in collection interface in collection interface there are some methods are there there are some methods are there okay yesterday I have uploaded this in your Google Classroom did you check the check with that guys did you check with that all these methods I told you all these methods which are present in collection interface all those methods which are present in collection interface can be used by all these child classes am I right or wrong yes come on guys tell me yeah we discussed that actually only we discussed yeah inheritance concept here now guys can you please check this method add method add method what is the use of this add method you know guys add method add method will add elements into your collection class for example please check this Al Dot add and here I am trying to Yale dot add and here I am trying to go with 10 like this I'm just passing a value guys that's it in the same manner I want to add remaining data also remaining data also just like this okay for example guys you know that you know that we can pass different types of data am I right or wrong like I told you collections will accept heterogeneous data right this is not int what is this guys what is this it is an very good summer very good Krishna very good Mukesh it is an integer integer yes integer wrapper class this is not inter okay now this is string all right guys let me just try to use null also null also after that just I'm passing some data guys just some data okay uh some 42 let me go with 10 and there's some 96 any some random data I'm just trying to pass some random data that's it not more than that okay like that yeah I can pass character also open that no problem just some random data any random data I can pass okay now I am trying to print my arraylist I'm just trying to print my error list that's it or else let me try to write like this here a y l i s t plus a l I'm just trying to print my error list okay now just let me go to my main method main method now inside my main method inside my main method new class EA dot a method one sir why we are getting like yellow color lines like this I'll explain you guys please wait for it I will explain you wait for it okay now let me execute my program right click run as Java application and this is my output this is my output right now guys I want to ask you a small question my first question is insertion order maintained or not insertion order insertion order means in which order I am entering in the same order the data is entered into my error list yes in scrt insertion what your order is maintained in such notaries maintain okay guys what about duplicates is duplicates allowed duplicates are allowed of course guys please observe here 10 10 yes duplicity duplicates are duplicates are allowed a l l o w e d duplicates are allowed what about null is null allowed is null allowed yeah of course of course null is alone null is also okay null is a load null is allowed not at all the trouble guys not at all trouble okay now now guys default default capacity default capacity of arraylist is 10.

[00:13:59]default capacity of arraylist is 10 okay after adding 10 elements I repeat default capacity of arraylist is 10. after adding 10 elements the capacity of the arraylist will be increased by half capacity of the arraylist will be increased by half guys half half that is current capacity into 3 by 2 plus 1.

[00:14:44]just let me try to write like this new capacity new capacity equal to current capacity current capacity into three by two plus one so generally what we will be saying you know the capacity of the like after filling 10 elements after filling 10 elements the capacity of the arraylist will be increased by half will be saying like that are you understanding me guys please tell me like if you can remember this formula find or else you can simply say you can simply say half means after for example 10 you have entered 10 elements if you are trying to enter one more element then it will be something like near to 15.

[00:15:42]15th guys are you getting me please tell me respond please respond in the chat please respond in the chat exactly exactly okay that nearly nearly 15 nearly 15 guys nearly 15. see according to the formula it will be 16. I'm not saying no for that if you remember the formula that is good if you are unable to remember the formula you can say like half it does not nothing to worry about it I hope you're understanding me guys okay right right now guys arraylist it is available from java 1.2 version arraylist is available from java 1.2 version 1.2 version onwards and most important point very very important point that is arraylist is let us go like this it is it is not synchronized by default a realist is not synchronized by default guys are you understanding me synchronization guys synchronous you you know that you know that upendra no 1.8 means not 18th version 1.8 is completely different 1.8 means Java eight okay guys when we came across synchronization concept did you remember when we came across synchronization concept synchronization concept we came across multi-threading uh exactly exactly Krishna exactly Mukesh multi-threading Summa yes multi-threading in multithreading we I mean in multiplayering we had considered like we have seen what is actually synchronization concept right so a realist is not synchronized by default not synchronizer by default means it is not thread safe it is not thread safe okay now guys I just want to ask you uh one more question here actually just a second just a second okay I want to ask you one more question here guys tell me arraylist will allows heterogeneous elements are only homogeneous elements can you please tell me arraylist will allows heterogeneous elements right yes obviously heterogeneous elements means any kind of data it heterogeneous heterogeneous elements are elements are alone heterogeneous elements are allowed right how many points here are there guys one two three four four five six seven eight nearly all these eight points you need to learn for remaining classes also linked list eight points Vector eight points has set all those eight points linked acid reset linkages map remap and hash table different different features will be there that is the only reason people will be getting confused but not my students I hope you're understanding me guys okay is it clear guys now now right so guys we'll do one thing we'll do one thing let me try to retrieve that data retrieve the data from error list now before retrieving the data from arraylist I want to use some methods guys okay there are some methods which are present in collections shall we use those methods for example size method system dot outdoor println system dot outdoor println I am using that size method Okay so plus a l dot size any idea any idea what can be possible expected output uh guys size you need to start with one or zero you need to start with one or zero length guys length length always starts with one okay one two three four five six seven eight nine let us check right click run as Java application sizes nine okay is empty is empty what that is empty method will be doing here you know right nine system dot out dot println system dot out dot println is empty method guys the return type of is empty method is Boolean Boolean okay it is going to return true it is going to return true if there are no elements in your hedonist so can you please tell me what is your expected output here to our phones false exactly let us check right click current has Java application false for example I am trying to use system.out.printerlin system dot outdoor print online clear okay sorry I'll be just going with clear okay now I am trying to use this is empty method now guys what this clear method will be doing you know clear method clear method clear method it will remove all the data it will remove all the data in the add a list so completely all these elements will be removed so guys right now what is our expect output here exactly t r u e true we should be getting our output as true am I clear with these guys please respond guys you need to respond don't sit idle please don't sit idle please respond okay now now guys there is this method no one more method that is contains object contains object okay so guys please observe here okay what I'll be trying to do you know what I'm trying to do you know I am trying to use system dot out dot println contains c-o-n-t-a-i-n-s contains method I'm trying to use contents method okay now please observe here plus plus a l dot contains and here just let me try to go with like Java Java okay now tell me guys what is my output true or false right now what is the output true or false guys please observe here right click run as Java application I'll be getting my output as false why why I'll be getting my output as false any idea yes right now there is no elements here all the elements are gone I had to clear the elements right right so let me do one thing guys let me try to keep them in comments let me try to keep them in comments like this okay now shall we check contains Java okay let us check right click run as Java application and I will be getting my output as true is it clear guys uh please tell me please respond please respond yes exactly exactly now guys do you know what actually there are other method like uh remove method is also there remove method like we can remove a specific element also okay for example we'll do one thing guys we'll do one thing system dot out dot println uh guys I want to remove this at 10 okay let us check this system dot out Dot println and I'm remov a Remo method remove method plus eal dot remove object 10 I'm trying to remove 10. okay now let me check right click run as okay here I'm just trying to after removing I'm trying to print my error list also now right click run as Java application guys what happened here what happened here I got an exception here yes why why I got an exception why I got an exception I want to remove my object okay but why I got an exception guys here here you are actually compiler is considering compiler is considering this 10 as index position it is considered in this 10 as index position okay are you understanding me guys okay guys we'll do one thing we'll do one thing where is this 10 present uh one I mean sorry zero one two three four five shall we give 5 and let us check guys are you understanding me let me try to give five here five okay let me check right click run as Java application guys is that value removed please tell me please tell me is that value removed guys observe it got removed yes it got removed now okay sir I want to do one thing okay system.out.print LM sir I don't want to go with index position can I go with directly object name also this is index I mean removing let me write like this Aria movie removing using index removing using index positions using index versions now I don't want to remove using index positions guys I want to remove by using this soundify object directly are you understanding me guys I just want to remove that but right now what I will be getting but if I execute my program what I will be getting I will be getting an exception so any ideas any ideas I don't want to use index position no no no no no I don't want to use how Krishna how how answer it completely how no I don't want to change the method come on upender I don't want to change the method Suma tell me how yeah how Krishna how guys actually what compiler is thinking you know no no no no what compiler is thinking you know compiler is thinking this as index position it is thinking this as an index position according to our opinion what it is foreign to our opinion what it is it is an object it is an object say to that compiler body that is not an index position that is instead an object type cast here Typecast that's it okay now please observe here right click run as Java application is 75 remote is it remote guys that's it that's it how you need to use that I mean typecasting the concept which you already learned okay now now guys do not actually there are some methods which are present in arraylist also yep there are some methods for example please check them add method it is already present in collection class yes I mean collection interface yes in arraylist also it is present for example add into position element object means if we want to add a particular element okay Al dot add guys I want to add I want to add 10 between Java and okay I'll do one thing I want to add 100 between Java and null between Java and null okay and now tell me guys 100 what should be the index position 100 what should be in the index equation exactly index position is 2 index portion is 2 and what is the element which I want to add I want to add 100 simple now please observe here please observe here system.out.printle and system.org println and here I am going with the arraylist and right click current as a Java application and I'll be able to add my element into my specific preferred location can you imagine adding like this in Array in array in Array can you prefer like this can you add like this 100 no if you are trying to add an element between two elements the next element is going to be moved to the other memory location no it will not move guys are you understanding me I hope you are getting me right for example for example if in Array okay 10 20 30 are there you want to add an element between 20 and 30 okay if you are trying to add 40 that 30 will be removed I'm right or wrong in the place of 30 you need to replace but here we are not replacing the element is just shifting I hope you're understanding me guys are you getting me guys that is the only reason that is the only reason performance wise collections are highly recommended highly recommended okay now like for example remove just now we have seen this remove method did we see the remove method remove we can remove like particular position we can remove a particular object and a size method also we have already seen that and get get in position for example please observe here guys system dot out Dot println I am trying to use get method okay get method please observe here a l dot get and I'm trying to give one uh tell me what is my output here what is my output here guys exactly exactly I will be I should be getting my output as Java so you understand what is use of get method and what is the use of size method am I right tell me now now guys do me a favor do me a favor okay system dot out Dot println system.out.intel and I just want to write okay driving the elements using for Loop retrieving the elements using for Loop okay uh for tell me tell me what I need to write okay obviously two semicolons okay now foreign first occurrence will be removed come on tell me okay I need to write into equal to zero okay fine no issues let me try to write int I equal to 0 after what I need to write after that what I need to write not length not length when there are when they're not length we are having we are having a Al dot size method right now here I should be less than l dot size less than l dot size now here after that I plus plus what do you say can you write like condition like this uh you need to help me out you need to help me out yes okay okay now can you please give me the code what I need to write inside this give me the code what I need to write yeah that is perfect Krishna that is perfect yes sushil yes Suma yes that is correct that is correct come on guys yeah print statement what what I need to print no open no nikhil no just please think please think I cannot print I guys if I'm trying to print the I only one two three four zero one two three four I'll be getting like this yeah Mukesh that is good guys system dot out dot println Al dot get get the method I need to use get method just now I told you right get method now please check this guys right click run as Java application are you seeing this yes in this way I can retrieve the elements from collections by using for Loop okay I want to do one thing guys I want to retrial the elements from collections that is by using for each Loop will you help me will you help me sir we don't want to help you uh come on here please please help me out please help me out ah tell me first firm uh after that no that is wrong that is completely wrong we cannot write like that Krishna we cannot write like that rathod guys how how you are writing how you will be writing India how you will be writing in Mukesh that is very good Suma that is very good very good very good come on think you remember the syntax of for each Loop right no wrong open the wrong guys generally in for each Loop in for each Loop first what okay let me just try to go with Colonia ah before that what we need to write before that what we need to write tell me data type I mean whatever the array which you are taking we need to take the data type now here I told you collections will not accept data types right what collections will accept what collections will I accept objects only objects so so can I write like this objact object o and Al yes now here remaining is same system oh right click run as Java application I'll be able to get my output like this is it clear guys for everyone guys come on here these are not data types these are objects here objects yes or no sir can I write arraylist error AI uh let me go with like arraylist and just let me go with like Oh Canada like this yes candidate like this please observe observe guys we are getting an error Mukesh right we need to type cast so this is not actually possible guys no we cannot write like that we cannot write like that okay we'll do one thing guys we'll do one thing uh sir I just want to have I'm having a small doubt can I go with integer integer guys can I go integer like this no why why because I'm having string elements also here right yeah we are having other data types like other objects okay sir uh is there any way is there any way that I want my arraylist to accept only integers guys please listen to my question correctly sir I want my arraylist to accept only int then why can't you use the array concept here why you are coming to collections uh sir array okay I can use array but in Array I have restriction for length am I right or wrong guys I'm having a drawback of length there is restriction formula so I don't want to worry about the length but I want my arraylist to accept only integers guys are you understanding me are you understanding me I don't want my arraylist to accept remaining objects I just want my arraylist to accept only integer is there any possibility yes from java 1.5 version onwards you are having this new feature that is generics here guys I'll be making my arraylist as i n t e g l integer and here also I'll be using integr integer like this now if I use this generics like this guys what is the use of this generics you know generics are used for type casting like to avoid to avoid the problems of type casting generics have been introduced in Java 1.5 version am I clear with this right now if you are giving a generic like this integer then our arraylist will accept only integers Did You observe line number 12 did you obserline number 12 guys come on come on guys we are getting an error we are getting an error right why because we have used generic here generates okay likewise you can use the string byte care float double Boolean any kind of generic you can use don't think like sir if you are using generics it became in a it became an array no guys see there are drawbacks of arrays for example if you are using generics only a particular object will be stored but when you are coming about methods we can use all those methods when you are speaking about the default capacity same how previously it is it has been implemented same capacity will be implemented like that yeah you can use objects also not really trouble guys am I clear with this we are getting an error at line number 12 because we have used generics now guys can we use integer here can we use integer here yep now please right click run as Java application and we'll be able to get an output like this uh sir I'm having a small doubt instead of integer can I use input can I use it uh sorry you told that when we are con like when we are discussing about wrapper classes you told that autoboxing and auto unboxing will be performed automatically automatically by the compiler so can we use int like this I'm expecting answers guys please respond please respond respond Still Still I need answers from someone yes okay guys some people are not some people almost everyone is saying we can use let me show you right click run as Java application can we use can we use actually yes guys guys hang on hang on actually yes when we can use the into you know when we can use hint you know if there is no null then you can use in no problem guys actually null is an object right so you cannot convert that into a primitive data type yes I hope you're understanding me if there is null is not there then fine you can use hint no issues am I clear with these guys enter or integer integer colon Al r just let me try to write o b j c t object oh sorry object or column Al like this did you understand uh this please tell me is it clear for everyone we can use like this we can use like this or we can use like this also you do understand the concept of generics please tell me guys please tell me you understand the concepts of generics no no see Roger don't go with null like zero okay it's the default value of an object that's it okay okay guys okay now now guys actually we can retry The Elements by using for Loop by using for each Loop by using for each Loop uh rupali yes for string that also we can retrieve it same as it is just string yes that's it not more than that okay now we'll do one thing guys we will try to retrieve the data by using iterator interface what do you say it or at or iterator intrac iterator interface okay now now guys please listen to me this is very very very very important please listen to me a l right eal I am trying to call iterator method okay iterator is a method which is present in arraylist what this iterator method will be doing you know iterator method will gives us a iterator interface just let me go with like I like this with the help of this iterator we can iterate the elements which are present in the arraylist guys not not normal English normal English guys iterator method iterator method what iterator method will be doing you know iterator method returns an iterator sir what is an iterator iterator means imagine like a cursor guys just imagine like a cursor which is present at the first position I mean which is present before the first element of your arraylist are you understanding me guys please tell me please tell me guys I mean for example guys for example what is the first element present in our arraylist as of now 10 right so iterator method will gives you iterator which is present here 10. with the help of that iterator now please observe here while while I'm using a method I dot I dot has next method has an extra method guys please this is very very very important here very very important now these are elements which are present in your arrays how many elements are there 10 uh 42 110 96 and 1. okay what guys please observe what iterator method will be doing you know iterator method will gives you an iterator which places the cursor before the first element okay right now where is the cursor present right now where is the cursor present before guys I need answers I need answers I literally need answers please tell me where is the cursor present before 10 ah very good before 10 now what has next method you know like what has next method will be doing you know guys has the next method is a method which is present in iterator okay what has next method will be doing has next method will check we'll just check before the cursor is there any element present yes or no yes or no guys come on here yes or no yes an element is present right then as the next method will return true it will return true if the condition is true system.out.printellent I dot next I am using this next method what this next method will be doing you know next method will return this 10 and the cursor will move to like this cursor will move to like this now guys are there any statements left behind in while loop no so the compiler will be again going to where the company will be going again it will be going to check the condition has an extra method uh tell me what has next method will give true or false just tell me true or false true why it is giving true why it is giving true because sir cursor before cursor you are having this 42 right so true okay enter into the loop system ah what next method will be doing what next method will be doing it will return 42 and the cursor will move to the next element guys are you understanding how the process will be going on after after one right now okay next method like this now guys has next method is there any element present after your cursor no so right now has next method will gives you false the loop will be terminated the loop will be terminated why we are getting like this oh hang on here here just I remove this from null okay let me keep like this now please observe here guys right click run as Java application this is how you will be you should be retrieving The Elements by using iterator interface did you got an idea guys please tell me that is great that is great and you know what actually we can use generics here also we can use generic scene also but if you want you can use or else no issues as simple as this okay now guys this is about arraylist easy or not tell me easy uh easy sir but uh exactly that butt is there now that will be cleared if you do practice can you do that for me guys please guys believe me believe me I'm not asking you more here later I'm not asking you more by Monday whenever you are coming to class on Monday please go through this program clearly okay that's it please have this program for me please have this program please check that check that Krishna check that at this particular point you need to check that please check that method is present in scanner class that is different come on Raja Rao don't forget that okay come on go ahead guys please write the program Guys these comments are very very very important comments please please don't miss those comments okay very important trust me in collections this I lost these comments only please don't miss those comments yet please don't miss those comments Mukesh generics came from 1.5 actually okay she can't wait for it wait for it please wait guys up to line number 24 complete for everyone no okay okay okay okay okay okay okay okay please please write this please right Ravi I want you to give me the line number Krishna in line number 21 you are just retraining the elements like you are trying to print the entire arraylist okay in line number 21 if you are trying to print arraylist how you will be getting your elements you know you will be getting your elements like this like a sit I mean like a group you cannot for example in line number 21 can you get this 42 down 10 down 96 down like that line by line you cannot do that you cannot do that do you understand the difference Krishna yes yes but yes uh okay I got a question from Ravi sir in the place of 12 can I add six plus six yeah why not foreign nothing will happen Ravi you can add okay buddy yes right um guys up to line number 30 I mean 29 complete for everyone line number 29 complete for everyone I am moving up I'm moving up three two one I'm moving up yeah I'll hold come on foreign okay sushil iterator does not copy the data from error list iterator retries the data from arraylist for example will for each copy the data from array no right exactly okay where it is present you know just okay let me show you please observe here this is a method right this method is present inside errorist foreign exactly what that method will be doing that method will generate it will gives you a iterator what is that use of that iterator iterator will iterates your cursor like that okay Suma I hope it's clear number all right guys is it done is it completed guys for everyone please respond in the chat okay this is the output guys this is the output like uh if you want you can write or else you can take a snapshot no problem I hope you have enjoyed our today's session yes foreign so guys do me a favor please please practice please practice guys please practice if you are not practicing collections it will test your patience now Krishna I will not post this program in the Google Classroom no not this program no way this program you need to practice if I copy this in the Google Classroom I know what you guys will do I don't want that okay so guys what I'm requesting is what I'm requesting is please practice this program at least for three times and Monday you will enjoy the class Monday guys Monday we'll be trying to go we'll be trying to complete linked list we'll be trying to complete Vector if time permits I'll be trying to complete set implementation classes also Monday Monday okay okay right guys right right always guys all right all right that's it guys that's it for today that's it for today I hope you have enjoyed our today's session we'll be trying to continue your session again by Monday and uh yes have a fantastic weekend and please don't forget to practice okay guys please don't forget to practice everyone have a great weekend guys enjoy with your family have a great weekend but please don't forget to practice right thank you thank you guys thank you thank you yeah yeah I know me yeah by the way thank you guys thank you good night everyone see you on Monday