Java SE Documentation Tutorials

I hope you’ve enjoyed your time and have learned all the fundamental concepts of Java. That’s because the page count property is marked as private and no other class except Book will be able to access it. Instead you’ll have to use one of the getters or setters. Now you can call the setName() method with whatever name you want to set to the user. Similarly, the setBirthDay() method can set the birthday. The getName() and getBorrowedBooks() are responsible for returning the value of the name and borrowedBooks variables.

To create array lists, you’ll need to import the java.util.ArrayList class at the top of your source file. Although you’ll use the primitive types most of the time, these wrapper classes will be handy in some scenarios we’ll discuss in a later section. This top level public class has to be named exactly the same as the source code filename. That’s why the file named Main.java contains the main class in this project. This is a public class, which means this class is accessible anywhere in the codebase. One Java source file (files with the .java extension) can contain only one top level public class in it.

How to Check if an Element Is Present or the Array List Is Empty

But do you remember the length() method you wrote inside the Book class? It’ll work for the regular books but will break in the e-books. Since the audio books don’t have any pages, setting the page count to zero can be an easy solution. Since the type of the borrowedBooks variable is not a concern of the Main class, the getter makes sure to return the value in the proper format. Since the properties have become private now, the System.out.println() line in the Main.java file will fail to directly access them and will cause an issue. You’ve already seen the keyword public multiple times.

Since the birthDay is a reference type, you’ll have to use the toString() method to print out on the console. In this system the users and the books can all be objects. These objects will have their own properties such as name and birthday (in case of a user) and title and author in case of the books. Just like in the array lists, the method doesn’t take any argument or return any value. Then you start by writing HashMap and then inside a pair of less than-greater than signs, you’ll write the data type for the key and the value. The lambda expression will then multiply the supplied value by 2 and print it out on the terminal.

What Are the Different Ways of Inputting and Outputting Data?

Selected tutorials have been printed; see the Related Resources box to the right. You’ve already learned about looping in previous sections. Well, array lists have a forEach() method of their own that takes a lambda expression as parameter and can perform an action on all the elements of the array list. Regular Expressions are a way to describe a set of strings based on common characteristics shared by each string in the set.

There are also other JVM (we’ll discuss what that means very soon) languages such as Kotlin, Groovy, Scala, and Clojure that you can use for different purposes. java se 7 tutorials It is an enterprise platform that is mainly used to develop web and enterprise applications. It includes topics like Servlet, JSP, Web Services, EJB, JPA, etc.