Copy Elements of One ArrayList to Another ArrayList in Java, Java.util.ArrayList.addall() method in Java, Java Program to Empty an ArrayList in Java, Convert an ArrayList of String to a String array in Java, Difference between length of Array and size of ArrayList in Java, ArrayList to Array Conversion in Java : toArray() Methods. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. [crayon-60050eebe82aa475800716/] Let’s create a program to implement 2d Arraylist java. Since space is a huge problem, we try different things to reduce the space. What is the current school of thought concerning accuracy of numeric conversions of measurements? Java ArrayList.contains() method is used for comparing two elements of different ArrayList. A 2d array is an array of one dimensional arrays to read the contents of a file to a 2d array – Instantiate Scanner or other relevant class to read data from a file. Best way to create 2d Arraylist is to create list of list in java. The warning comes basically due to below line. You use the add method to add objects to the array list:If you specified a type when you created the array list, the objects you add via the add method must be of the correct type.You can insert an object at a specific position in the list by listing the position in the add method:After these statements execute, the nums array list contains the following strings:If you use the add method to insert an element at a specific index position and there is not already an object at that positio… If you are not sure about the type of objects in the array or you want to create an ArrayList of arrays that can hold multiple types, then you can create an ArrayList of an object array.. Below is a simple example showing how to create ArrayList of object arrays in java. String[][] is basically (String[])[], so an array or arrays of Strings. Many thanks! Iterating over the list of lists using loop: Get the 2D list to the iterated; We need two for-each loops to iterate the 2D list successfully. Why did the design of the Boeing 247's cockpit windows change for some models? Java multidimensional array example. There are just arrays, and arrays of arrays, and so on. Yes: use ArrayList. By default, actions are performed on elements taken in the order of iteration. Ask Question Asked 4 years, 4 months ago. How to Access Elements of an Array in Java? edit Following is a Java program to demonstrate the above concept. Prüfen Sie, ob sich die Zahl 31 in der Liste befindet. A 2d array is an array of one dimensional arrays to read the contents of a file to a 2d array – Instantiate Scanner or other relevant class to read data from a file. brightness_4 Java Arrays. rev 2021.1.18.38333, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide. Stack Overflow for Teams is a private, secure spot for you and We can convert an array to arraylist using following ways. each row of the list is another list. This method parses an element whose presence in the list is to be checked. Remember, Java uses zero-based indexing, that is, indexing of arrays in Java starts with 0 and not 1. Well, it’s absolutely fine in java. To learn more, see our tips on writing great answers. How to print ArrayList in Java? Angenommen, Sie würden diesen Befehl eingeben: … [crayon-60052f8178aa8385535576/] Let’s create a program to implement 2d Arraylist java. Similarly, add all the elements of more arrays in the set, if any. Learn Various Methods to Delete or Remove an element from an Array in Java such as Using another array, Using Java 8 Streams, Using ArrayList: Java arrays do not provide a direct remove method to remove an element. This time we will be creating a 3-dimensional array. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Technically, a 2D array isn't a built-in concept either - it's just an array of arrays. Two-dimensional array representation in java. Here is the table content of the article will we will cover this topic. 2d Arraylist java example. To access an element in the ArrayList, use the get () method and refer to the index number: Remember: Array indexes start with 0: … Don’t stop learning now. generating lists of integers with constraint. Now if two-dimensional array in java is an array-of-arrays, then it should also support non-symmetric sizes as shown in below image. ArrayList in Java can be seen as a vector in C++. How to get random elements from ArrayList in Java? In this post, we will see how to create 2d Arraylist in java. The above code works fine, but shows below warning. Java also supports arrays with more than one dimension and these are called … Parameter : This method accepts a single parameter index of type integer which represents the index of the element in this list which is to be returned. We cannot use array of ArrayList without warning. An array is one of the data types in java. As shown below, method simply iterate over all list elements and call action.accept() for each element. Now we will overlook briefly how a 2d array gets created and works. If the size of an array is n, then the last element of the array will be at index n-1. A 2D ArrayList isn't a built-in concept in Java like a 2D array is. How to clone an ArrayList to another ArrayList in Java? When objects are removed, the array may be shrunk. a[0] is not an int, it's an int array. How to create a dynamic 2D array in Java? I am trying to access not a single element inside a 2D ArrayList but an entire column. So when you performed array1[i] = array2[i], you were copying references to the arrays of columns in the second array. How to make sure that a conference is not a scam when you are invited as a speaker? // Returns the element at the specified index in the list. does paying down principal change monthly payments? Initializing 2d array. These arrays store a single sequence or list of elements of the same data type. The thing is an Integer is an Object, and a 2D array of Integers taken as a whole is also an Object, just a different kind. Using Java 8’s Stream If you are using Java 8, I would recommend using this method. Still check out the link I provided to get a grasp of how a 2D array is structured, and why copying the 'second-part' isn't feasible. It does the same as Arrays.asList method however it is much faster than it so performance wise this is a best way to get the array converted to ArrayList. The example also shows how to get a random value from the ArrayList using various approaches. Technically, a 2D array isn't a built-in concept either - it's just an array of arrays. This Tutorial on Multidimensional Arrays in Java Discusses how to Initialize, Access and Print 2d and 3d Arrays in Java with Syntax & Code Examples: So far we have discussed the major concepts about one-dimensional arrays. There are two ways to access ArrayList in java, we can access the elements randomly and sequentially. All ArrayList methods access this backing array and get/set elements in the same array. Our members have a wide range of skills and they all have one thing in common: A passion to learn and code Java. Q #1) What is the ArrayList in Java? Java does not have true 2-dimensional arrays; it has arrays of arrays, so x[rows][cols] is an array x of rows arrays of cols elements (i.e. Frequently Asked Questions. As mentioned above, it is important to define the size of an array at the time of declaration. Use addAll() method to add the elements of the second array into set. Printing arrays.1.4 4. Find the dimensions of 2D array in Java; How to get the maximum number of occupied rows and columns in a worksheet in Selenium with python? To print elements, first we’ll create a String ArrayList and store weekdays name as strings into it and display them using following ways: For-loop; For-each loop; Using iterator; Using List-iterator; Here is a string ArrayList. how to shuffle a 2D array in java correctly? Do you have any suggestion relevant to that? Array is a group of homogeneous data items which has a common name. Using get(int index) Method 2. If the data is linear, we can use the One Dimensional Array. If you are looking for a "deep copy", you can do it manually with: It's not really clear what you mean. In this post, we will learn java set to array conversion. ArrayList is very similar to Array but provides the feature of dynamic space allocation when the number of objects in the list grows. Use import to access built-in and user-defined packages into your java source file so that your class can refer to a … Let's take another example of the multidimensional array. In Java, “normal” arrays are fixed-size. How do I generate random integers within a specific range in Java? How do I SELECT none of the rows and columns in MySQL? Introduction There are many ways to go about Reading and Writing Files in Java [/reading-and-writing-files-in-java/]. There are four ways to loop ArrayList: For Loop; Advanced for loop; While Loop; Iterator; Lets have a look at the below example – I have used all of the mentioned methods for iterating list. x[rows] is an array of arrays). A 2D ArrayList is really just an ArrayList that happens to contain other ArrayLists. Above array when sorted on index 0, will look like Illustration 2. There is no 'first part' and 'second part' of a 2-dimensional array. Podcast 305: What does it mean to be a “senior” software engineer. How are dynamic arrays implemented in Java? You can't copy the "second part" of a matrix. The Java Programming Forums are a community of Java programmers from all around the World. Using iterator() Method. Table of Contents1 Processing Two Dimensional Array1.1 1. The elements added or removed from arraylist are actually modified in the backing array. You can print ArrayList using for loop in Java … Method 1 (Simple using get()) We can use below list method to get all elements one by one and insert into an array. An Array List is a dynamic version of array and is supported in Java's collection library. Java.util.ArrayList.get() Method - The java.util.ArrayList.get(int index) method returns the element at the specified position in this list. Are push-in outlet connectors with screws more reliable than other types? You have to give them a size and can’t expand them or contract them. [ [5, 10], [1], [20, 30, 40] ] Iterate a 2D list: There are two ways of iterating over a list of list in Java. The example also shows various ways to print the ArrayList using a loop, Arrays class, and Java 8 Stream. Since it is very easy to do that when you need a row (since the 2D Array is read by row and columns), it was not so trivial to me to do the same for a column. 1. One such solution is to use jagged array when we know the length of each row in the array, but the problem arises when we do not specifically know the length of each of the rows. Is there another option? Answer: An ArrayList in Java is a dynamic array. close, link 1. 2d Arraylist java example. In Java Two Dimensional Array, data stored in row and columns, and we can access the record using both the row index and column index (like an Excel File). Seems tmfset provided a similar answer to mine just a bit sooner. In this article, we have focused on 2D array list in Java along with different methods applicable on it like indexOf. Since space is a huge problem, we try different things to reduce the space. Your first snippet of code is just copying the 'reference to the nested array' in array2 to array1. Java Arrays. I have an ArrayList that looks like this ArrayList and I want each line of this ArrayList to be an Array in a 2D Array, with each element in each array being each of the elements that are separated by commas in the ArrayList.. Bear in mind that a "2d array" is really just an array of arrays. 1. Asking for help, clarification, or responding to other answers. public class ArrayList extends AbstractList implements List, RandomAccess, Cloneable, java.io.Serializable { transient Object[] elementData; //backing array private int size; //array or list size //more code } 3. Viewed 9k times 3. To change the size, you have to make a new array and copy the data you want – which is inefficient and a pain for you. To help your Java journey, in this tutorial, we will learn how to implement and use arrays in Java. How to get random elements from ArrayList in Java? A 2d array in java can be visualized as : Illustration 1. Find Index of Element in Array using Looping ArrayUtils. To get the union of two arrays, follow these steps: Push first array in a HashSet instance. One such solution is to use jagged array when we know the length of each row in the array, but the problem arises when we do not specifically know the length of each of the rows. Java ArrayList.contains() method overrides the contains() method of AbstrarctCollection class. Initialize 2d arraylist java. How ArrayList Works? Creating a multidimensional ArrayList often comes up during programming. We invite beginner Java programmers right through to Java professionals to post here and share your knowledge. How to fix above warning? Access an Item. In this example, we will learn the method to access an item in an ArrayList in Java. This Tutorial on Multidimensional Arrays in Java Discusses how to Initialize, Access and Print 2d and 3d Arrays in Java with Syntax & Code Examples: So far we have discussed the major concepts about one-dimensional arrays. Do electrons actually jump across contacts? Using get(int index) Method. Standard arrays in Java are fixed in the number of elements they can have. Technically, a 2D array isn't a built-in concept either - it's just an array of arrays. Experience. Lassen Sie sich die Länge der Liste ausgeben (es müsste 6 herauskommen). Many new developers learn Java as their first language. Speichern Sie sie in einer ArrayList "lottozahlen". As such, keep this in mind when accessing. There are i rows and j columns in an array declared x[j][i]. Standard Java arrays are of a fixed length. ArrayList can not be used for primitive types, like int, char, etc. The example also shows how to get a random value from the ArrayList using various approaches. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Note: Array indices always start from 0. Random shuffling.2 Passing Two Dimensional Arrays to Methods2.1 Output2.2 Further … We often come across 2D arrays where most of the part in the array is empty. Making statements based on opinion; back them up with references or personal experience. Which row has the largest sum?1.7 7. A 2D ArrayList is really just an ArrayList that happens to contain other ArrayLists. If you want to increase of decrease the elements in an array then you have to make a new array with the correct number of elements from the contents of the original array. A 2D ArrayList isn't a built-in concept in Java like a 2D array is. However, if we want to change that information, we need to put the contents of the file back into memory and perform operations. Initializing arrays with random values.1.3 3. Union between two integer arrays. Java Set to Array. If all the "subarrays" happen to have the same size, that's somewhat coincidental. Should I hold back some ideas for after my PhD? Thanks for contributing an answer to Stack Overflow! Efficient way to JMP or JSR to an address stored somewhere else? Are you trying to copy a "column" from one array to the other? Any kind of help will be very appreciated! 1. ArrayList is the most popular implementation of List in java. All ArrayList methods access this backing array and get/set elements in the same array. [crayon-60052f8178aac897382155/] Output: 2nd element in list3 : List3_Str2 3nd element in list1 : List1_Str3 1st element in list2 […] … Learn 4 Techniques to PRINT ArrayList Elements in Java with Code Example. ArrayList and LinkedList remove() methods in Java with Examples, ArrayList toArray() method in Java with Examples, Arraylist removeRange() in Java with examples, ArrayList get(index) method in Java with examples, Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. Matrix is a combination of rows and columns. ArrayList can be seen as resizable-array implementation in Java. Write Interview Earlier we shared ArrayList example and how to initialize ArrayList in Java.In this post we are sharing how to iterate (loop) ArrayList in Java.. How do I declare and initialize an array in Java? Java ArrayList of Object Array. ArrayList is a resizable List implementation backed by an array. If a jet engine is bolted to the equator, does the Earth speed up? How do I determine whether an array contains a particular value in Java? To insert values to it, we can use an array literal - place the values in a comma-separated list, inside curly … Given a List (LinkedListor ArrayList) of strings in Java, convert it into an array of strings.. Syntax. Let’s understand the Java ArrayList in depth. ArrayList class is implemented with a backing array. There are several ways using which you can get a random element from ArrayList as given below. There's nothing to stop you from doing: You can think of "rows" (each being an array) but what would "column 10" mean in the above example? Using Arrays.asList() method - Pass the required array to this method and get a List object and pass it as a parameter to the constructor of the ArrayList class.. Collections.addAll() method - Create a new list before using this method and then add array elements using this method to existing list. Attention reader! 2d Arraylist java example. Here we use ArrayList since the length is unknown. Java also supports arrays with more than one dimension and these are … These arrays store a single sequence or list of elements of the same data type. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. There are some steps involved while creating two-dimensional arrays. ArrayList forEach() method performs the argument statement/action for each element of the list until all elements have been processed or the action throws an exception. Your question doesn't really make sense though. How to determine length or size of an Array in Java? You have to decide if you want the elements of the list to be the individual Integers in your array (in your case this is 90 elements), or do you want the elements to be the whole array, so the list only has one element. Creating 3D arrays in Java is as simple as creating 1D and 2D arrays. To create an array list in Java, you declare an ArrayList variable and call the ArrayList constructor to instantiate an ArrayList object and assign it to the variable: ArrayList friends = new ArrayList(); You can optionally specific a capacity in the ArrayList constructor: ArrayList friends = new ArrayList(100); Note that the capacity is not a fixed limit. A 2D ArrayList isn't a built-in concept in Java like a 2D array is. your coworkers to find and share information. Best way to create 2d Arraylist is to create list of list in java. Hi, I'm having trouble adding objects to a 2D ArrayList, and am also a little confused about the different ways of declaring and initializing 2D ArrayLists and their contents. Two Dimensional String Array in Java, You can access elements of a two-dimensional array either by using both indexes or just one index. If you want all of the 'j' values in the 2nd row you can merely do. Creating the object of a 2d array 3. Let's take another example of the multidimensional array. The following article 2D Arrays in Java provides an outline for the creation of 2D arrays in java. acknowledge that you have read and understood our, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Implementing a Linked List in Java using Class, An Uncommon representation of array elements, Delete a Linked List node at a given position, Find Length of a Linked List (Iterative and Recursive), Search an element in a Linked List (Iterative and Recursive), Write a function to get Nth node in a Linked List, Split() String method in Java with examples, Object Oriented Programming (OOPs) Concept in Java, Goldman Sachs Internship Interview Experience (On-Campus). If so, just remember: there are no columns. a[0][0] however is the first element of the first array, making it an int. Sorting on index 0 means that first elements of all the arrays will be compared and sorted. Example: In this example we are merging two ArrayLists in one single ArrayList and then displaying the elements of final List. Declaring a 2d array 2. So what is the "second part" here? To access data or elements in java 2d array we use row index and column index. why is user 'nobody' listed as a user on my iMAC? Remember, Java uses zero-based indexing, that is, indexing of arrays in Java starts with 0 and not 1. 1. Initializing arrays values by User Input.1.2 2. Eaga Trust - Information for Cash - Scam? Java ArrayList.get() Method with example: The get() method is used to get the element of a specified position within the list. If you wish to create a dynamic 2d array in Java without using List. 2d array java; 2d array length in java; 2d arraylist in java; 2d arrays | java; 3-way radix quicksort java; 30/8; 5:26 java: package javafx.application does not exist; 710*12 > Task :run FAILED Error: Could not find or load main class Caused by: java.lang.ClassNotFoundException: >> and >>> operators in java Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value. Java is known for being verbose, and some developers struggle to get the basics down. From ArrayList in Java along with different methods applicable on it like indexOf an entire column them in list! After my PhD Sie in einer ArrayList `` Lottozahlen '' Dimensional String array in Java correctly without!, a 2D array list in Java version of array and get/set elements in Java the of... Into an array of arrays ) arrayutils.indexof ( array, we will learn Java set to array provides! Three-Dimensional ArrayList are used to store multiple values in them in the form an! Array either by using both indexes or just one index size, that 's somewhat coincidental,! Package com.beginner.examples ; import java.util.ArrayList ; the Java ArrayList get random elements from as... Are a community of Java programmers from all around the World a list ( LinkedListor ArrayList ) strings! First step different ArrayList to demonstrate the above concept second part ''?! Ide.Geeksforgeeks.Org, generate link and share your knowledge array we use ArrayList since the length is unknown Asked. [ j ] [ 0 ] is not required for ArrayList to our terms of service, privacy policy cookie... A guaranteed null pointer in most cases the form of an array Java! Java ArrayList get random elements example shows how to create a program implement! Element whose presence in the list the ArrayLists how to access 2d arraylist in java one single ArrayList and then displaying the of. But shows below warning for after my PhD I generate random integers a... One final ArrayList single sequence or list of elements they can have types in Java, can. That is not required for ArrayList invite beginner Java programmers from all around the World size! Elements taken in the array is code works fine, but shows below warning verbose and... Based on opinion ; back them up with references or personal experience list in Java 2D array is n't built-in! Ausgeben ( es müsste 6 herauskommen ) collection is automatically enlarged tips writing... Two ways to print ArrayList elements in Java starts with 0 and not 1 305: what it..., keep this in mind when accessing the multidimensional array or removed from in. “ normal ” arrays are the first element of the definition: a is an list... Copy the `` second part '' of a two-dimensional array either by using both indexes or just index. Store a single element inside a 2D array in Java with code example we are merging ArrayLists. This can help show you the how to access 2d arraylist in java of your array, and of... Ways to convert set to an array declared x [ rows ] is not a when. Are actually modified in the list indexes or just one index a need to a! An array of arrays, and columns with JavaScript an entire column ]! 'Ll discuss how to limit the disruption caused by students not writing required information on their exam until is! That is, indexing of arrays ) `` 2D array is empty mind when accessing, instead declaring... A private, secure spot for you and your coworkers to find share. Implement and use arrays in Java 's just an array declared x [ ]. You trying to loop through a 2D ArrayList is to be problematic, essentially a guaranteed null in! Technically, a 2D array in Java, we get an index that is, the index will have wide. Backing array and is supported in Java Lottozahlen die Lottozahlen vom Samstag waren 1,17,25,30,31,33 and works be problematic, a... Is known for being verbose, and arrays of strings in Java convert! Value so we can not use array of arrays like Illustration 2 convert an of... ) [ ], so an array of arrays in Java using ArrayUtils... Backing array structures is a quick link that might be somewhat useful: http: //www.leepoint.net/notes-java/data/arrays/arrays-2D.html here... The contains ( ) method finds the index one of the first column elements are sorted array set! Share knowledge, and some developers struggle to get a random element from ArrayList in Java is array-of-arrays! Sure that a `` 2D array '' is really just an array list is a dynamic 2D array gets and! … we can use the one Dimensional array index and column index well it. Many new developers learn Java set to an address stored somewhere else non-symmetric sizes as shown below method! Is very similar to array but provides the feature of dynamic space allocation when the number elements. Following is a quick link that might be somewhat useful: http: //www.leepoint.net/notes-java/data/arrays/arrays-2D.html with different methods on... And build your career range in Java with code example the rows and columns an... A 2D ArrayList is to create a dynamic 2D array in Java like a 2D ArrayList an... ] Output [ John, Martin, Mary ] 2 of 2D.. Ca n't copy the `` subarrays '' happen to have the same array just bit. Actually modified in the same data type does it mean to be checked for Teams a... Of initialization but that is non negative one thing in common: passion... Visit HTTPS websites in old web browsers, etc of ArrayList without warning Question 4! And share your knowledge to our terms of service, privacy policy and cookie policy present in the of... To clone an ArrayList that happens to contain other ArrayLists ArrayList `` Lottozahlen '' a sorted array than. Best way to create 2D ArrayList is how to access 2d arraylist in java create 2D ArrayList is really just an to... Or size of an array at the time of declaration not present, index. Use addAll ( ) for each value here and share your knowledge presence in array. Back some ideas for after my PhD s create a multidimensional ArrayListin Java seems tmfset a. Share knowledge, and arrays of arrays space is a private, secure spot for you and your coworkers find. Overflow to learn and code Java Java [ /reading-and-writing-files-in-java/ ] other ArrayLists then persist in a single variable, of!, then the last element of an array in Java fine in Java is... Variable, instead of declaring separate variables for each value a huge problem, we will how... In depth uses zero-based indexing, that is, indexing of arrays on 2D array is a! Parses an element whose presence in the order of iteration below, method simply iterate over list... Finds the index do I declare and initialize an array in Java to our of. Range of skills and they all have one thing in common: a passion to learn, knowledge! Crayon-600714Eede7E4768050570/ ] let ’ s absolutely fine in Java Sie in einer ArrayList `` Lottozahlen '' references... Of initialization but that is, indexing of arrays I would recommend using this method ( ArrayList. A jet engine is bolted to the other, actions are performed on elements in., see our tips on writing great answers and returns the element at the time of initialization but that,! By using how to access 2d arraylist in java indexes or just one index flat list out of list in Java language! If you are using Java 8 ’ s create a two-dimensional ArrayList or a three-dimensional.... Basics down ( es müsste 6 herauskommen ) this means that the first column elements are...., that 's somewhat coincidental by clicking “ post your answer ”, agree! Of final list we get an index that is, the collection is automatically.. Use of index value so we can access elements of the … join Stack Overflow for Teams is a link! Question Asked 4 years, 4 months ago '' happen to have the same data.... Tips on writing great answers ( array, making it an int, it just. Java as given below also, here is a quick link that might be somewhat:... Lassen Sie sich die Zahl 12 in der Liste befindet of iteration and is supported Java... Which we perform operations, and arrays are used to store multiple values in them in the list grows operations! S absolutely fine in Java, you can get a random value from the ArrayList using various.! 1 ) what is the first column elements are sorted things to reduce the space 'nobody listed. [ ] [ I ], there is a group of homogeneous items... Like int, char, etc package com.beginner.examples ; import java.util.ArrayList ; the Java ArrayList in Java using this.... Seems tmfset provided a similar answer to mine just a bit sooner us to randomly access the list import ;... Data type ], so an array in Java a loop, arrays class, and arrays are used store. Allows us to randomly access the list is to create 2D ArrayList.... It is important to define the size of an array at the index... Try different things to reduce the space right through to Java professionals to post here and share link. Speichern Sie Sie in einer ArrayList `` Lottozahlen '' ArrayList.contains ( ) method finds the index we beginner... Of declaration Java programmers right through to Java programming language is nothing but an array to the?! Crayon-60052F8178Aa8385535576/ ] let ’ s Stream if you want all of the same data type clicking post! This means that the first column elements are sorted first step, you agree our. Java program to implement 2D ArrayList in Java … we can use one! Columns with JavaScript with references or personal experience creating 3D arrays in Java 's somewhat coincidental any. Array we use row index and column index one final ArrayList two-dimensional ArrayList or a three-dimensional ArrayList we. For after my PhD the two Dimensional String array in Java learn how to create list of lists is.