There are many ways to copy an array in Java. Here, we will explore the following: Using the clone() method Using System.arraycopy() Using the Arrays.copyOf() Copy an array in Java using the clone() method This is the most used way of cloning objects. The clone() method belongs to Object class, and we can use it to…
Read More Copy an Array 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 iterate over JsonNode in Java. JsonNode class is the base class for all JSON nodes, which form the basis of Jackson’s JSON Tree Model. How to iterate over JsonNode in Java? To loop through the JsonNode, we need to use the Java Iterator interface. Here is an example program…
Read More Iterate over JsonNode in JavaJackson is a popular Java library that provides powerful tools for converting JSON objects to Java objects and vice versa. In this tutorial, we will explore the different ways of mapping JSON objects to Java objects using Jackson. We’ll also look at how to handle dynamic JSON objects and cover some useful Jackson annotations that…
Read More Master Mapping JSON Objects to Java Objects with JacksonSometimes we need to consume HTTPS endpoints that do not have valid certificates. We can do that by configuring the Java HttpClient to accept all SSL certificates, even from an untrusted Certificate Authority. Here you will see how to communicate with HTTPS endpoint that may not have a valid SSL certificate. In the following example,…
Read More Java HttpClient – Accept all SSL Certificatesimport org.apache.http.HttpResponse; import org.apache.http.HttpHeaders; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.client.methods.RequestBuilder; import org.apache.http.impl.client.BasicResponseHandler; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import java.io.IOException; public class Test { public static void main(String[] args) throws IOException { try (CloseableHttpClient httpclient = HttpClients.createDefault()) { HttpUriRequest request = RequestBuilder.get() .setUri(“https://jsonplaceholder.typicode.com/todos/1”) // adding headers .setHeader(HttpHeaders.CONTENT_TYPE, “application/json”) .setHeader(“Authorization”, “Bearer 123token”) .build(); System.out.println(“Executing GET request…”); HttpResponse response = httpclient.execute(request);…
Read More Add a Custom HTTP Header with the HttpClientpublic class Test { public static void main(String[] args) { Integer[] array = new Integer[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; // reverse an array Integer[] reversedArray = reverse(array); // print the elements Arrays.stream(reversedArray).forEach(item -> System.out.print(item + ” “)); } public static Integer[] reverse(Integer[] array) { List arrayList = Arrays.asList(array); Collections.reverse(arrayList); return…
Read More Reverse an Array in Javapublic 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 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(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)); System.out.println(numbers.stream().mapToInt(Integer::intValue).average().getAsDouble()); } } Output: 5.5 Here, we used the mapToInt(Integer::intValue) to convert the Stream<Integer> which is the result of the stream() method, to IntStream. import java.util.*; public class…
Read More Find the Average of Numbers in Javapublic class Test { public static void main(String[] args) { int[] array = new int[]{7, 1, 9, 2, 5}; Arrays.sort(array); Arrays.stream(array).forEach(System.out::print); } } Output: 1 2 5 7 9 Note: values of type int will be automatically converted to the corresponding Wrapper class. And since the Integer Wrapper class implements Comparable, we can sort…
Read More Sort an Array 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 Javaclass Test { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, “Java”); map.put(7, “Python”); map.put(10, “Ruby”); map.put(3, “Kotlin”); for (Map.Entry<Integer, String> entry : map.entrySet()) { System.out.println(“Key = ” + entry.getKey() + “, Value = ” + entry.getValue()); } } } Output: Key = 1, Value = Java Key = 3,…
Read More Iterate over a Map in Javapublic class Test { public static void main(String[] args) { // create an object of Random class Random random = new Random(); // Generate random integer 0 to 100 int randomInteger1 = random.nextInt(101); // Generate random integer 0 to 10000 int randomInteger2 = random.nextInt(10001); // Generate random double value double randomDouble = random.nextDouble(); // Generate…
Read More Generate a Random Number in Java