Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Regression testing is an important step in the release process, to ensure that new code doesn't break the existing functionality. As the codebase evolves, we want to run these tests frequently to help catch any issues early on.
The best way to ensure these tests run frequently on an automated basis is, of course, to include them in the CI/CD pipeline. This way, the regression tests will execute automatically whenever we commit code to the repository.
In this tutorial, we'll see how to create regression tests using Selenium, and then include them in our pipeline using GitHub Actions:, to be run on the LambdaTest cloud grid:
1. Introduction
In this quick tutorial, we’ll demonstrate several ways to use a console for user input and output in Java.
We’ll have a look at a few methods of the Scanner class for handling input, and then we’ll show some simple output using System.out.
Finally, we’ll see how to use the Console class, available since Java 6, for both console input and output.
2. Reading from System.in
For our first examples, we’ll use the Scanner class in the java.util package to obtain the input from System.in — the “standard” input stream:
Scanner scanner = new Scanner(System.in);Let’s use the nextLine() method to read an entire line of input as a String and advance to the next line:
String nameSurname = scanner.nextLine();We can also use the next() method to get the next input token from the stream:
String gender = scanner.next();If we’re expecting numeric inputs, we can use nextInt() to get the next input as an int primitive, and, similarly, we can use nextDouble() to get a variable of type double:
int age = scanner.nextInt();
double height = scanner.nextDouble();The Scanner class also offers hasNext_Prefix() methods which return true if the next token can be interpreted as a corresponding data type.
For example, we can use hasNextInt() method to check if the next token can be interpreted as an integer:
while (scanner.hasNextInt()) {
int nmbr = scanner.nextInt();
//...
}Also, we can use the hasNext(Pattern pattern) method to check if the following input token matches a pattern:
if (scanner.hasNext(Pattern.compile("www.baeldung.com"))) {
//...
}Besides using the Scanner class, we can also use an InputStreamReader with System.in to get the input from the console:
BufferedReader buffReader = new BufferedReader(new InputStreamReader(System.in));And then we can read input and parse it to an integer:
int i = Integer.parseInt(buffReader.readLine());
3. Writing to System.out
For console output, we can use System.out — an instance of the PrintStream class, which is a type of OutputStream.
In our example, we’ll use console output to provide a prompt for user input and display a final message to a user.
Let’s use the println() method to print a String and terminate the line:
System.out.println("Please enter your name and surname: ");Alternately, we can use the print() method, which works similarly to println(), but without terminating the line:
System.out.print("Have a good");
System.out.print(" one!");4. Using the Console Class for Input and Output
In JDK 6 and later, we can use the Console class from java.io package to read from and write to the console.
To obtain a Console object, we’ll call System.console():
Console console = System.console();Next, let’s use the readLine() method of the Console class to write a line to the console and then read a line from the console:
String progLanguauge = console.readLine("Enter your favourite programming language: ");
If we need to read sensitive information, such as a password, we can use the readPassword() method to prompt a user for a password and read the password from the console with echoing disabled:
char[] pass = console.readPassword("To finish, enter password: ");
We can also use the Console class to write output to the console, for example, using the printf() method with a String argument:
console.printf(progLanguauge + " is very interesting!");
5. Conclusion
In this article, we showed how to use several Java classes to perform console user input and output.
