How to Declare an Array in Java?
dataType[] arr; Where: int[] intArray = new int[5]; String[] arr = new String[3]; arr[0] = “value 1”; arr[1] = “value 2”; arr[2] = “value 3”;
Read More How to Declare an Array in Java?Author: alegru
Java Synchronized Blocks and Methods
synchronized void method() {} public class SynchronizedInstanceMethodExample implements Runnable { public static void main(String[] args) { SynchronizedInstanceMethodExample runnable = new SynchronizedInstanceMethodExample(); new Thread(runnable).start(); // creates one thread new Thread(runnable).start(); // creates second thread } // Inherited run method from the Runnable interface @Override public void run() { try { // Calling the non-synchronized method print()…
Read More Java Synchronized Blocks and MethodsPrint Array Elements in Java
class PrintArrayElementsExample { public static void main(String[] args) { int[] arr1 = {1, 7, 9, 5, 2, 8, 3}; String[] arr2 = {“Megan”, “Tom”, “Melissa”, “John”, “Steve”}; // print elements of the arr1 System.out.println(Arrays.toString(arr1)); // print elements of the arr2 System.out.println(Arrays.toString(arr2)); } } Output: [1, 7, 9, 5, 2, 8, 3] [Megan, Tom, Melissa, John,…
Read More Print Array Elements in JavaSplit a comma-separated String in Java
public class SplitString { public static void main(String[] args) { String names = “Tom,Steve,John,Megan,Melissa”; // split string String[] arr = names.split(“,”); // print the size of the array System.out.println(arr.length); // print the elements Stream.of(arr).forEach(System.out::println); } } Output: 5 Tom Steve John Megan Melissa If you need a list, instead of an array, use the…
Read More Split a comma-separated String in JavaHow to Schedule a Task in Spring Boot
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.scheduling.annotation.EnableScheduling; @EnableScheduling @SpringBootApplication public class ScheduledDemoApplication { public static void main(String[] args) { SpringApplication.run(ScheduledDemoApplication.class, args); } } import org.springframework.scheduling.annotation.Scheduled; import org.springframework.stereotype.Component; @Component public class ScheduledTaskService { @Scheduled(fixedRate = 5000) public void execute() { // some logic that will be executed on a schedule System.out.println(“Code is being executed…”); } } Output:…
Read More How to Schedule a Task in Spring BootRead a File From the Resources Folder in Spring Boot
some data in a file import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.core.io.ClassPathResource; import org.springframework.core.io.Resource; import org.springframework.util.FileCopyUtils; import java.io.*; import java.nio.charset.StandardCharsets; @SpringBootApplication public class DemoApplication { public static void main(String[] args) throws IOException { SpringApplication.run(DemoApplication.class, args); readFile(); } public static void readFile() throws IOException { // read a file Resource resource = new ClassPathResource(“classpath:data.txt”); // get inputStream…
Read More Read a File From the Resources Folder in Spring BootHow to break out of the loop in Java?
class BreakOutOfLoop { public static void main(String[] args) { int[] arr = {1, 2, 3, 4, 5}; // iterate over array for (int i = 0; i < arr.length; i++) { if (arr[i] == 3) { // break out of the loop if the current value is equals to 3 System.out.println(“Breaking out of the loop!”);…
Read More How to break out of the loop in Java?Check if Array Contains a Value in Java
class CheckIfArrayContainsValue { public static void main(String[] args) { String[] programmingLanguages = {“Python”, “Kotlin”, “Ruby”, “JavaScript”, “C#”, “Java”, “Flutter”}; for (String lang : programmingLanguages) { if (lang.equals(“Java”)) { System.out.println(“It does contain!”); break; // value found, exit the loop } } } } Output: It does contain! Here, we are iterating over the array, and…
Read More Check if Array Contains a Value in JavaConvert InputStream to a String in Java
Output: Some String Here, we put the creation of the Scanner object into a try-with-resources because we want to close the Scanner after it reads all the data. We passed the “\\A” to tell the Scanner to read the entire input stream. import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.nio.charset.StandardCharsets; class ConvertInputStreamToString { /** *…
Read More Convert InputStream to a String in JavaFind duplicate elements in an Array in Java
class FindDuplicateElements { public static void main(String[] args) { int[] array = new int[]{2, 4, 7, 2, 11, 5, 7, 14, 22, 11, 49, 58, 14, 101, 1, 3, 205, 49, 101, 12}; for (int i = 0; i < array.length; i++) { // outer loop for (int j = i + 1; j <…
Read More Find duplicate elements in an Array in JavaEscape Double Quotes in Java String
class EscapeDoubleQuotesInString { public static void main(String[] args) { String str = “Hello, I’m \”Steve\” and I am \”Java\” developer”; System.out.println(str); } } Output: Hello, I’m “Steve” and I am “Java” developer Escape double quotes in a JSON object in Java There are many cases where you might need to escape double quotes. In this…
Read More Escape Double Quotes in Java StringRead and write Excel files in Java
<dependency> <groupid>org.apache.poi</groupid> <artifactid>poi-ooxml</artifactid> <version>5.0.0</version> </dependency> If you are not familiar with Maven, you can check out this tutorial: Create Java Project with Maven. import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; @Data @AllArgsConstructor @NoArgsConstructor public class Product { private int id; private String color; private String size; private int cost; private String description; } import org.apache.poi.ss.usermodel.Cell;…
Read More Read and write Excel files in JavaTesting with StepVerifier in Project Reactor
<dependency> <groupid>io.projectreactor</groupid> <artifactid>reactor-test</artifactid> <version>3.1.0.RELEASE</version> <scope>test</scope> </dependency> class ReactiveJavaTutorialTest { @Test public void testFlux() { //Create a Flux Flux <Integer> fluxToTest = Flux.just(1, 2, 3, 4, 5); // Create a test StepVerifier.create(fluxToTest) .expectNext(1) .expectNext(2) .expectNext(3) .expectNext(4) .expectNext(5) .expectComplete() // we expect Flux to complete after sending the number 5 which is the last element .verify(); }…
Read More Testing with StepVerifier in Project ReactorImplementing Backpressure in Project Reactor
class ReactiveJavaTutorial { public static void main(String[] args) { Flux<String> cities = Flux.fromIterable( new ArrayList<>(Arrays.asList(“New York”, “London”, “Paris”, “Toronto”, “Rome”))); cities.log().subscribe(); } } Output: INFO 6832 — [ main] reactor.Flux.Iterable.1 : | onSubscribe([Synchronous Fuseable] FluxIterable.IterableSubscription) INFO 6832 — [ main] reactor.Flux.Iterable.1 : | request(unbounded) INFO 6832 — [ main] reactor.Flux.Iterable.1 : | onNext(New York) INFO…
Read More Implementing Backpressure in Project ReactorsubscribeOn and publishOn operators in Project Reactor
class ReactiveJavaTutorial { public static void main(String[] args) { Flux<String> cities = Flux.just(“New York”, “London”, “Paris”, “Amsterdam”) .map(String::toUpperCase) .filter(cityName -> cityName.length() <= 8) .map(cityName -> cityName.concat(” City”)) .log(); cities.subscribe(); } Output: INFO 14040 — [main] reactor.Flux.MapFuseable.1 : | onSubscribe([Fuseable] FluxMapFuseable.MapFuseableSubscriber) INFO 14040 — [main] reactor.Flux.MapFuseable.1 : | request(unbounded) INFO 14040 — [main] reactor.Flux.MapFuseable.1 : |…
Read More subscribeOn and publishOn operators in Project Reactor