Want to learn how to merge two ArrayLists in Java? In this post, we will cover the following ways: Using the List.addAll() method Using the Java 8 Streams Using the ListUtils.union() method Merge two ArrayLists in Java using the List.addAll() method There is addAll() method from the List interface that appends all of the elements in…
Read More How to merge two ArrayLists in Java?In this post, you will learn how to Serialize and Deserialize an ArrayList in Java using the FileOutputStream and FileInputStream classes. How to Serialize an ArrayList in Java? Serialization is the process of changing the state of an object into a byte stream. For example, we use it to write some Java objects into a file. In…
Read More Serialize and Deserialize an ArrayList in JavaIn one of the previous examples, we covered how to sort an ArrayList in ascending order. In this post, you will learn how to sort ArrayList in descending order in Java. We will explore the following ways: Using the sort() method Using the Collections.sort() and Collections.reverse() methods Sort ArrayList in descending order in Java using the…
Read More Sort ArrayList in descending order in JavaWe often need to compare two ArrayList in Java. In this post, you will learn how to do that in two ways: Using the ArrayList.equals() method Using the CollectionUtils.isEqualCollection() method Compare two ArrayList in Java using the ArrayList.equals() method The ArrayList.equals() method compares two ArrayList. It compares the sizes of the lists, elements equality, and the…
Read More Compare two ArrayList in JavaIn this post, you will learn how to convert ArrayList to an Array in Java using two methods: With a for loop Using toArray() method Convert ArrayList to Array in Java with a for loop In this example, we create an empty array, then iterate over the list and add each element to the array. class Test {…
Read More Convert ArrayList to Array in JavaThere are many ways to convert an array to a list in Java. In this tutorial, we will cover the following: Using the Arrays.asList() method Using Java 8 Streams API Using the List.of() method Convert array to list in Java using the Arrays.asList() method We can use the asList() method from the Arrays class, which belongs to…
Read More Convert Array to List in JavaWe often need to convert a list to a map in Java. In this lesson, you will learn how to do that with Java 8. If you are looking for more information on working with maps in Java, check out our tutorial on Map in Java. Let’s say we have a list of User objects. …
Read More Convert List to Map in JavaIn this lesson, you will learn how to convert a JSON array to a Java list. We will use the ObjectMapper class from the Jackson library. Let’s say we have a JSON that is an array of objects: [ { “name”:”John”, “grade”:8, “city”:”Boston” }, { “name”:”Tom”, “grade”:9, “city”:”Denver” }, { “name”:”Megan”, “grade”:8, “city”:”New York city”…
Read More Convert a JSON array to a list with Java Jacksonpublic class Test {z public static void main(String[] args) { List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)); Collections.reverse(numbers); System.out.println(numbers); } } Output: [10, 9, 8, 7, 6, 5, 4, 3, 2, 1] Reverse a List using List.add() and List.remove() methods public class Test { public static void main(String[]…
Read More Reverse a List in Javapublic Object get(int index); import java.util.*; public class Test { public static void main(String[] args) { List<String> cities = new ArrayList<>(Arrays.asList(“New York”, “London”, “Paris”, “Chicago”, “Rome”)); // retrieve the second element from the list System.out.println(cities.get(2)); // retrieve the 4th element from the list System.out.println(cities.get(4)); } } Output: Paris Rome Lists are zero-based indexes, which means that the…
Read More Get the Element from an ArrayList in Javaimport java.util.*; public class Test { public static void main(String[] args) { List<String> names = new ArrayList<>(Arrays.asList(“Megan”, “Tom”, “Steve”, “Megan”, “Meliisa”, “Tom”, “John”)); Set<String> uniqueNames = new HashSet<>(names); // creating a Set from the List System.out.println(uniqueNames); } } Output: [Megan, Tom, Steve, John, Meliisa] Remove duplicates from a List in Java using the Java 8…
Read More Remove Duplicates from a List in Javaimport java.util.*; public class Test { public static void main(String[] args) { List<Integer> numbers = new ArrayList<>(Arrays.asList(7, 12, 5, 28, 97, 14, 2, 7, 8, 12, 19, 22)); Collections.sort(numbers); System.out.println(numbers); } } Output: [2, 5, 7, 7, 8, 12, 12, 14, 19, 22, 28, 97] Using the sort() method from ArrayList class public class Test…
Read More Sort a List in Javapublic class Test { public static void main(String[] args) { List<Integer> list = new ArrayList<>(Arrays.asList(7, 19, 14, 1, 12, 22, 18, 3, 28, 5)); System.out.println(“Maximum value: ” + Collections.max(list)); System.out.println(“Minimum value: ” + Collections.min(list)); } } Output: Maximum value: 28 Minimum value: 1 Finding the maximum and minimum values in List using the Java 8…
Read More Find Max and Min Values of a List in JavaLinkedList<String> list = new LinkedList<>(); List<Integer> list = new LinkedList<>(); class Test { public static void main(String[] args) { List<String> list = new LinkedList<>(); list.add(“Steve”); list.add(“Megan”); list.add(“Melissa”); list.add(“Ryan”); System.out.println(list); } } Output: [Steve, Megan, Melissa, Ryan] class Test { public static void main(String[] args) { List<String> list = new LinkedList<>(); list.add(“Steve”); list.add(“Megan”); list.add(“Melissa”); list.add(“Ryan”); List<String>…
Read More LinkedList in JavaArrayList<String> list = new ArrayList<>(); List<Integer> list = new ArrayList<>(); class Test { public static void main(String[] args) { List<String> list = new ArrayList<>(); list.add(“Steve”); list.add(“Megan”); list.add(“Melissa”); list.add(“Ryan”); System.out.println(list); } } Output: [Steve, Megan, Melissa, Ryan] Using the addAll() method, we can add all the elements of an existing list to the newly created…
Read More ArrayList in Java