Java ArrayList Length and Size
Java ArrayList does not publicly expose the length of the backing array, and only the count of the stored elements can be retrieved using its size() method.
In Java, an ArrayList is a dynamic data structure that extends the functionality of arrays. Unlike traditional arrays, ArrayLists can dynamically resize themselves, allowing you to add or remove elements without worrying about the size.
ArrayLists are part of the Java Collections Framework and are available in the java.util package.
Related Tags
Tutorials
Java ArrayList Sort: Ascending and Descending Order
Learn to sort Java ArrayList in ascending and descending order using ArrayList.sort(), Collections.sort(), Comparator interface and Java 8 Streams.
Correct Way to Assert Two Equal Lists Ignoring Order
Comparing two Java lists with order ignored is a common requirement during JUnit tests where both lists come from different sources.
Create and Initialize List with Values in One Line
A Java List can be initialized in various ways. However, initializing a list with multiple elements can be a tedious task. This tutorial will discuss different techniques to initialize a list in one line to make your work easy and reduce boilerplate code. Method List Attributes Java Version List list …
Remove All Occurrences of Element from a List
Learn to remove all the occurrences of an element from a given List using Java loops, list methods and Stream API.
How to Flatten a Nested List in Java
Flattening a nested list may seem hard at the beginning, but it’s not. It can be easily done using only plain Java, streams, or external libraries.
Java Arrays.asList() vs new ArrayList()
Learn to create a List from array using Arrays.asList(array) and new ArrayList(Arrays.asList(array). Learn their differences with examples.
Java ArrayList: A Comprehensive Guide for Beginners
Java ArrayList class represents a resizable array of objects which allows us to add, remove, find, sort and replace elements.
Java List
Lists are the core building blocks of the Collections framework. These tutorials will teach us the basics of different List classes in Java.
Remove Duplicates from a List or ArrayList in Java
Learn to remove duplicate elements from an ArrayList using different techniques such as HashSet, LinkedHashSet, and using Java 8 stream.
Java ArrayList spliterator() Example
Since Java 8, Spliterators are a special type of iterator that supports parallel iteration of portions of the source such as list, set, or array.
ArrayList removeIf(): Remove Elements Matching a Condition
Java ArrayList.removeIf() removes all elements that satisfy a condition by iterating through the elements and matching against the specified Predicate.
Java ArrayList replaceAll()
ArrayList replaceAll() transform each element in the list by applying a lambda expression or UnaryOperator implementation.
Java List retainAll()
In Java, the ArrayList.retainAll() retains only those elements in this list that are contained in the specified collection. Rest all elements are removed from the list. This method is exactly the opposite to removeAll() method. 1. Syntax The syntax to use the retainAll() method is: Method Argument – a collection …
Java ArrayList removeAll(): Remove All Occurrences of Element
ArrayList removeAll() removes all of matching elements that are contained in the specified method argument collection. It removes all occurrences of matching elements, not only first occurrence.
Java ArrayList remove(): Remove a Single Element from List
ArrayList remove() removes the first occurrence of the specified element from this list, if it is present, else the list remains unchanged.
Java ArrayList.listIterator()
Java ArrayList.listIterator() returns a bi-directional list iterator that iterates over the elements of the current list.
Java ArrayList forEach()
ArrayList forEach() method iterate the list and performs the argument action for each element of the list until all elements have been processed.
Java ArrayList clone() and Deep Copy Example
ArrayList.clone() creates a shallow copy of the given ArrayList. Learn to create deep copy and shallow copy of an arraylist with examples.
Java ArrayList.addAll() – Add Multiple Items to a List
Java ArrayList.addAll() appends all of the elements of argument collection to the list at the end or the specified index position.
Java ArrayList add() – Add a Single Element to List
The ArrayList.add() in Java adds a single element to the list, either at the end of the list or at the specified index position. Always use generics for compile-time type safety while adding the element to the arraylist. 1. ArrayList.add() Method The add() method first ensures that there is sufficient …
Difference between LinkedList vs. ArrayList in Java
Java LinkedList and ArrayList are different in many aspects, and we need to understand both to decide when to use which class.
Java Vector vs ArrayList
In Java, ArrayList and Vector, both implement java.util.List interface and provide the capability to store and get objects within using simple API methods. Still, they are different in many aspects, and we need to understand both classes in detail to make a wise decision about when to use which class. …
Convert Set to List in Java and Vice-versa
Learn to convert a Set to List in Java using constructor, addAll() and Java 8 streams. Learn to convert list to set to remove duplicates.
Convert an Array to Mutable, Immutable and Unmodifiable Lists
Learn different and useful ways to convert array to list in Java. Learn to use Java 9 List, Java 8 Stream, Collections and Guava library.
Convert LinkedList to ArrayList in Java and Vice-versa
Learn to convert LinkedList to ArrayList in Java with example. We will also learn to convert arraylist to linkedlist in Java.
Java ArrayList.toArray()
Learn to convert ArrayList to an array using toArray() method. The toArray() returns an array containing all of the elements in the list.
Check if Element Exists in an ArrayList in Java
ArrayList contains() method is used to check if the specified element exists in the given arraylist or not. If element exist then method returns true.
Java ArrayList.ensureCapacity()
Learn to use ArrayList ensureCapacity() method to increase the capacity of already initialized arraylist to a desired size. It improve performance of list.
Replace an Existing Item in ArrayList
Learn to update or replace an existing element in ArrayList with a new specified element or value, using set (int index, Object newItem) method. 1. Replacing an Existing Item To replace an existing item, we must find the item’s exact position (index) in the ArrayList. Once we have the index, …
Check if an ArrayList is Empty in Java
Learn to check if an ArrayList is empty using isEmpty() and size() methods. Note isEmpty() method internally checks the size of the list.
Clear ArrayList with clear() vs. removeAll()
Learn to clear arraylist or empty an arraylist in Java. Clearing a list means to remove all elements from the list. Difference between clear and removeAll.
How to Merge Two ArrayLists in Java
Learn how to merge two arraylists into a combined single arraylist in Java. Also learn to join arraylists without duplicates in the combined list.
Serialize and Deserialize an ArrayList in Java
Learn to serialize and/or deserialize an ArrayList in Java with easy-to-follow examples. Note that the list items must also be Serializable.
How to Swap Two Elements in an ArrayList in Java
Learn to swap two specified elements in ArrayList in Java. We will use Collections.swap() method to swap two elements within a specified arraylist at specified indices. 1. Collections.swap() API The Collections.swap() method swaps the elements at the specified positions in the specified list. The index arguments must be a valid …
Synchronized ArrayList in Java
Learn to synchronize an ArrayList using either Collections.synchronizedList() or CopyOnWriteArrayList class with examples.
How to Compare Two Lists in Java
Learn to compare two arraylists in Java with List Items. Learn to test whether two arraylists are equal and then find different list items.
ArrayList get() – Get Element at Index
Learn how to get the element from an ArrayList. We will be using ArrayList.get() method to get the object at the specified index of the arraylist.
Java Arraylist.indexOf()
Learn to get the index of the first occurrence of an element in an arraylist in Java using ArrayList.indexOf() method with a simple example.
Java Arraylist.lastIndexOf()
Learn to get the index of last occurrence of an element in the arraylist in Java using Arraylist.lastIndexOf() method with a simple example.
Java ArrayList subList()
Learn to get a sublist from an existing ArrayList using ArrayList.subList() and modify the original list using the sublist view.
Add Multiple Elements to ArrayList in One Line
The Java ArrayList class is part of the Collection framework and is an implementation of a resizable array data structure. It automatically grows and shrinks when elements are added or removed in the runtime, whenever required, This Java tutorial discussed the different ways to add multiple items to an ArrayList …
Remove Element(s) from ArrayList in Java
Learn to remove element from ArrayList. Remove element at specifed index, or element value. Remove all elements from arraylist for spcified value example.
Add Element(s) at Specified Index to ArrayList in Java
Java programs to add single or multiple elements at the specified index of arraylist with ArrayList.add() and addAll() methods.
Different Ways to Iterate an ArrayList
The Java iterate through ArrayList programs. Learn how to retrieve values from ArrayList in Java using for loop, while loop, iterator and stream api.
Initialize an ArrayList in Java
Java ArrayList can be initialized in one line using List.of(), and new ArrayList constructors. Learn to add elements one by one and in bulk.