The size member function.
myList.size();
http://docs.oracle.com/javase/6/docs/api/java/util/ArrayList.html
Answer from Adam Reed on Stack OverflowOracle
docs.oracle.com › javase › 8 › docs › api › java › util › ArrayList.html
ArrayList (Java Platform SE 8 )
April 21, 2026 - This class is a member of the Java Collections Framework. ... Constructs an empty list with the specified initial capacity. ... Constructs an empty list with an initial capacity of ten. ... Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator. ... Trims the capacity of this ArrayList instance to be the list's current size.
W3Schools
w3schools.com › JAVA › ref_arraylist_size.asp
Java ArrayList size() Method
compare() equals() sort() fill() length Java ArrayList Methods ·
java - How to find the length of an array list? - Stack Overflow
I don't know how to find the length of an array list. I think you might need to use blank.length(); but I'm not sure. I made an array list ArrayList myList = new ArrayList More on stackoverflow.com
why in java does an array use length and an arrayList use Size?
The number of elements in an array can't change, so an array object (yes, arrays are objects) can have a public final field length (though they could have called it size, they didn't) The number of elements in a Collection (ArrayList implements the Collection interface) can change (so it can't be immutable), so an accessor method is used: size() (though they could have called it length(), they didn't) More on reddit.com
4
0
June 20, 2016List vs Array vs ArrayList
These are three different things: Array - a very basic data structure. It has a fixed, predetermined size that must be known at the time of creating (instantiating) the array. Think of it as a sorting box with several slots. Here, you have .length - without parentheses as it is a property, not a method List - an interface (not a class) that defines certain behavior. It cannot be instantiated on its own. ArrayList - a concrete class that implements the List interface. When you see a declaration like List data = new ArrayList<>(); there are several things going on: Listprogramming against the interface - here, the interface List is used as data type - this is good practice as it allows you to at any time change the internal representation of the List - e.g. from ArrayList to LinkedList if you figure out that the other better suits your needs. this is a data type identifier. It limits the type of elements that can be stored in the list. Here, only String objects are allowed. If you were to omit this, the list would store Object (the ancestor of all Java classes) and descendant instances (i.e. Object and any subclass of it). data - just the variable name new - the keyword to create a new Object Instance ArrayList<>() - the constructor call. Here, the constructor without parameters of the ArrayList class is called. The diamond operator <> is used to infer (take) the data type for the ArrayList from the variable type (here String). So, the whole is: we create a new variable of type List that can only accept String elements and ist internally represented as ArrayList. More on reddit.com
15
7
September 12, 2023[Java] How to write .size() method for an ArrayList?
Look ar ArrayList's implementation, create your own class, and implement the most useful methods(add,get,remove,size). It should be pretty straightforward. As you'll see, there is a private variable size, that increases and decreases when you add/remove an object. More on reddit.com
16
7
April 30, 2013Videos
02:55
ArrayList size() method in Java | How to find ArrayList length ...
03:01
ArrayList size() method in Java | Java ArrayList size() | Get the ...
03:56
How to find the size of an ArrayList in Java (Core Java Interview ...
04:09
ArrayList Size Capacity | ArrayList In Java | List | Collection ...
Why ArrayList Uses .size() Instead of .length in Java? | Array ...
04:45
ArrayList length(size) in java example - YouTube
GeeksforGeeks
geeksforgeeks.org › java › java-program-to-find-the-length-size-of-an-arraylist
Java Program to Find the Length/Size of an ArrayList - GeeksforGeeks
July 11, 2025 - This method does not take any parameters and returns an integer value which is the size of the ArrayList. ... // Java program to find the size // of an ArrayList import java.util.*; public class GFG { public static void main(String[] args) throws Exception { // Creating object of ArrayList<Integer> ArrayList<Integer> arrlist = new ArrayList<Integer>(); // Populating arrlist arrlist.add(1); arrlist.add(2); arrlist.add(3); arrlist.add(4); arrlist.add(5); // print arrlist System.out.println("ArrayList: " + arrlist); // getting total size of arrlist // using size() method int size = arrlist.size(); // print the size of arrlist System.out.println("Size of ArrayList = " + size); } }
Top answer 1 of 2
275
The size member function.
myList.size();
http://docs.oracle.com/javase/6/docs/api/java/util/ArrayList.html
2 of 2
42
System.out.println(myList.size());
Since no elements are in the list
output => 0
myList.add("newString"); // use myList.add() to insert elements to the arraylist
System.out.println(myList.size());
Since one element is added to the list
output => 1
TheServerSide
theserverside.com › blog › Coffee-Talk-Java-News-Stories-and-Opinions › Java-array-size-explained-by-example
Java array size, length and loop examples
June 10, 2025 - The size or length count of an array in Java includes both null and non-null characters. Unlike the String and ArrayList, Java arrays do not have a size() or length() method, only a length property.
GeeksforGeeks
geeksforgeeks.org › java › arraylist-size-method-in-java-with-examples
ArrayList size() Method in Java with Examples - GeeksforGeeks
July 11, 2025 - Example 1: Here, we will use the size() method to get the number of elements in an ArrayList of integers. ... // Java program to demonstrate the use of // size() method for Integer ArrayList import java.util.ArrayList; public class GFG { public ...
Baeldung
baeldung.com › home › java › java array › the capacity of an arraylist vs the size of an array in java
The Capacity of an ArrayList vs the Size of an Array in Java | Baeldung
November 11, 2025 - We’ll also look at examples of when we should initialize ArrayList with a capacity and the benefits and disadvantages in terms of memory usage. To understand the differences, let’s first try both options. In java, it’s mandatory to specify the size of an array while creating a new instance of it: Integer[] array = new Integer[100]; System.out.println("Size of an array:" + array.length); Here, we created an Integer array of size 100, which resulted in the below output ·
BeginnersBook
beginnersbook.com › 2013 › 12 › how-to-find-length-of-arraylist-in-java
How to find length of ArrayList in Java
Initial size: 0 Size after few additions: 5 Size after remove operations: 3 Final ArrayList: 1 45 99
Codecademy
codecademy.com › docs › java › arraylist › .size()
Java | ArrayList | .size() | Codecademy
January 27, 2023 - The .size() method of the ArrayList class returns the number of elements in the list. ... Looking for an introduction to the theory behind programming? Master Python while learning data structures, algorithms, and more! ... Learn to code in Java — a robust programming language used to create ...
iO Flood
ioflood.com › blog › length-of-arraylist-java
Java ArrayList Length: How to Get the Size of an ArrayList
February 27, 2024 - Always ensure that your ArrayLists are well-structured and appropriately sized for your needs. And remember, the size() method is your friend when you need to determine the length of an ArrayList, even in a multi-dimensional context. Java 8 introduced a powerful new concept called Streams, which can also be used to determine the length of an ArrayList.
W3Schools
w3schools.com › java › java_arraylist.asp
Java ArrayList
It is part of the java.util package and implements the List interface. The difference between a built-in array and an ArrayList in Java, is that the size of an array cannot be modified (if you want to add or remove elements to/from an array, you have to create a new one).
Quora
quora.com › What-is-the-default-size-of-ArrayList-in-Java
What is the default size of ArrayList in Java? - Quora
Answer (1 of 3): The Default Size of ArrayList is 10 . Once ArrayList reaches its capacity a new ArrayList will be created with new capacity = ( current capacity * 3 /2 ) + 1 . Advantage : Array List is the Best Choice for Retrieval Operations Because of Array List Class Implements Random Acces...
TheServerSide
theserverside.com › blog › Coffee-Talk-Java-News-Stories-and-Opinions › How-do-I-find-the-Java-array-length
How do I find the Java array length?
To find the size of a Java array, make sure you invoke the length property, not the method. To determine the size of an array in your code, you need to use the Java array’s length property field.
Medium
medium.com › @mertercan › should-we-specify-the-initial-size-of-an-arraylist-in-java-5a948aadd52d
Should we specify the initial size of an ArrayList in Java? | by Naci Mert ERCAN | Medium
July 31, 2022 - Every time call the method, the ArrayList size increases by 50% of the current size. private int newCapacity(int minCapacity) { // overflow-conscious code int oldCapacity = elementData.length; int newCapacity = oldCapacity + (oldCapacity >> 1); if (newCapacity - minCapacity <= 0) { if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) return Math.max(DEFAULT_CAPACITY, minCapacity); if (minCapacity < 0) // overflow throw new OutOfMemoryError(); return minCapacity; } return (newCapacity - MAX_ARRAY_SIZE <= 0) ?
Reddit
reddit.com › r/learnprogramming › why in java does an array use length and an arraylist use size?
r/learnprogramming on Reddit: why in java does an array use length and an arrayList use Size?
June 20, 2016 - Actually, ArrayList has a size() method because that's what the Collection interface specifies to name the method that returns the number of elements in the collection. They picked size() instead of length() because Collections are not necessarily ordered, so length is less meaningful than size.
Reddit
reddit.com › r/javahelp › list vs array vs arraylist
r/javahelp on Reddit: List vs Array vs ArrayList
September 12, 2023 -
Coming from Python, this whole Java thing is incredibly confusing. The thing is, they don't seem to mix and uses different methods such as .size() vs .length(). All of them also seem to be doing the same thing: having a group of something.
I really need a comparison of the three, and how to declare, manipulate, and access, etc them.
Top answer 1 of 5
16
These are three different things: Array - a very basic data structure. It has a fixed, predetermined size that must be known at the time of creating (instantiating) the array. Think of it as a sorting box with several slots. Here, you have .length - without parentheses as it is a property, not a method List - an interface (not a class) that defines certain behavior. It cannot be instantiated on its own. ArrayList - a concrete class that implements the List interface. When you see a declaration like List data = new ArrayList<>(); there are several things going on: Listprogramming against the interface - here, the interface List is used as data type - this is good practice as it allows you to at any time change the internal representation of the List - e.g. from ArrayList to LinkedList if you figure out that the other better suits your needs. this is a data type identifier. It limits the type of elements that can be stored in the list. Here, only String objects are allowed. If you were to omit this, the list would store Object (the ancestor of all Java classes) and descendant instances (i.e. Object and any subclass of it). data - just the variable name new - the keyword to create a new Object Instance ArrayList<>() - the constructor call. Here, the constructor without parameters of the ArrayList class is called. The diamond operator <> is used to infer (take) the data type for the ArrayList from the variable type (here String). So, the whole is: we create a new variable of type List that can only accept String elements and ist internally represented as ArrayList.
2 of 5
4
Array An array is a data structure built into the Java language which can hold a number of elements, all of the same type. It cannot be resized once it has been created, and you cannot add elements to it without specifying an index. // creates an array of 10 ints int[] arr = new int[10]; // sets the value of the 0th element to 5 arr[0] = 5; // prints the value of the 0th element, which is 5 System.out.println(arr[0]); // Sets e to the value of the 0th element of arr, which is 5 int e = arr[0]; // Sets the value of the 1st element to 6 arr[1] = 6; // prints the length of arr System.out.println(arr.length); // even though arr[9] has not been set, // all elements initialize to 0 when first created System.out.println(arr[9]); /* Illegal operations! */ // an exception is thrown since arr can only hold 10 elements System.out.println(arr[11]); // there is no shorthand syntax to get the last element of an array System.out.println(arr[-1]); // length is a variable, not a method System.out.println(arr.length()); // arr can only hold ints arr[2] = "Hello"; List A List is an class that is part of the Java Standard Library which allows for dynamic insertion and deletion of elements. You can't just create a List though, you have to use one of its subclasses, which includes ArrayList, and you have to use generics as well. Think of an ArrayList as a dynamic version of an array, and is the closest thing to Python's list datatype. // Make sure to import these at the top of your class! import java.util.List; import java.util.ArrayList; // creates an ArrayList of ints List myList = new ArrayList<>(); // adds 5 to myList myList.add(5); // prints the 0th element of myList, which is 5 System.out.println(myList.get(0)); myList.add(6); // removes the last element of myList, which is 6 int removed = myList.remove(); // prints the size of the list, which is 1 System.out.println(myList.size()); /* Illegal operations! */ // myList only has 1 element System.out.println(list.get(5)); myList.remove(); // removes 5 // throws an exception since the list is empty myList.remove(); // throws an exception since myList can only take ints myList.add("Hello"); // you can only use bracket notation on arrays System.out.println(myList[0]); // size is a method, not a variable System.out.println(myList.size); Other Info There are lots of other List subclasses you can use depending on the kind of operations you want to do on it, such as Queues, LinkedLists, and PriorityQueues. The reason why we use Integer instead of int when working with Lists is a limitation of the Java language. Generic types can only be object types, but primitive types, such as int, double, boolean, etc., are not object types, and thus we have to use autoboxing to work with primitives in this manner.
W3Schools
w3schools.com › java › java_list.asp
Java List
The List interface is part of the Java Collections Framework and represents an ordered collection of elements. You can access elements by their index, add duplicates, and maintain the insertion order. Since List is an interface, you cannot create a List object directly. Instead, you use a class that implements the List interface, such as: ArrayList - like a resizable array with fast random access
Reddit
reddit.com › r/learnprogramming › [java] how to write .size() method for an arraylist?
r/learnprogramming on Reddit: [Java] How to write .size() method for an ArrayList?
April 30, 2013 -
I have an ArrayList and I need to override the .size() method to get the size. Any help would be appreciated
Top answer 1 of 5
5
Look ar ArrayList's implementation, create your own class, and implement the most useful methods(add,get,remove,size). It should be pretty straightforward. As you'll see, there is a private variable size, that increases and decreases when you add/remove an object.
2 of 5
3
I might be wrong, but ArrayList's size() method does that already, doesn't it?
Careers360
careers360.com › home › online courses & certifications › articles
Array Length in Java: A Comprehensive Guide
May 21, 2025 - While the official method is ‘size()’, you will often hear developers speak of the "Java ArrayList length." The length of ArrayList in Java is the same as its size, determined by the number of elements it contains.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Array › slice
Array.prototype.slice() - JavaScript | MDN
Negative index counts back from the end of the array — if -array.length <= end < 0, end + array.length is used.