تثبيت IntelliJ IDEA وجولة فيه

Written Explanation

What an IDE gives you

A text editor only edits text. An IDE knows the language you are writing, and that knowledge appears as help:

• Error highlighting: a mistake such as a missing semicolon is underlined while you type, before you compile anything.
• Code completion: as you type a name, the IDE offers matching choices.
• Run and debug buttons: one click compiles and runs the program, with output shown in the same window.
• Project view: all the files of a project are displayed as a tree, with search and navigation.

None of this changes the language or the compiler. Under the hood the IDE uses the same JDK that you installed. It only presses the buttons for you. A learner who understands the manual route (javac, then java) will understand what the IDE does, and will be able to fix things when the IDE misbehaves.

Which edition, and where to get it

This course uses IntelliJ IDEA, made by JetBrains. Older course notes talk about the free Community Edition. JetBrains has since announced that, starting with version 2025.3, the two editions became one unified product, with the core features that Community offered remaining free to use. That is what JetBrains' announcement states, as reported in the sources listed below. Because download pages change, do this:

1. Open the official JetBrains IntelliJ IDEA download page in your browser.
2. Choose your operating system (Windows, macOS, or Linux) and your processor type if asked, such as Intel or Apple Silicon on a Mac.
3. Pick the free option if the page offers a choice between free use and a paid or trial subscription. If a prompt asks you to sign in for a trial, you can usually skip it. Core Java work does not need the paid features.
4. Run the installer, or on macOS drag the app to Applications, or on Linux follow the page's instructions for your system. Accept the defaults unless you have a reason to change them.

Paid features are not needed for this course, and if you are unsure whether a feature is free, ignore it for now.

The first launch: the Welcome screen

When no project is open, IntelliJ shows the Welcome screen. JetBrains documents that the Welcome screen appears when you close all open projects. From it you can create a new project, open an existing one, or pick a recent one.

Creating your first project

JetBrains' tutorial for a first Java application gives these steps. Read them as a pattern, because labels may change by version:

1. On the Welcome screen click New Project. If a project is already open, use File, then New, then Project.
2. In the dialog, choose Java and give the project a name, for example hello-ide. Note the location: it is the folder where the project will live. Use the course folder from lesson 1.
3. Make sure the build system is set to IntelliJ. (Build tools such as Maven and Gradle come later in the course.)
4. In the JDK field, select the JDK you installed in lesson 2. If the list shows it, choose it. If it is installed but not listed, use the option to add a JDK from disk and point to the JDK's root folder. If you do not have one, the dialog can download one, but you already have one.
5. Leave the "add sample code" option off for this lesson, so that you create the class yourself and see every step. The option name may differ in your version.
6. Click Create.

IntelliJ opens the project window and shows a project tree on the left, with a folder called src. Source files go there.

Adding a class and running it

In the Project tool window, select the src folder, then use the New menu (right-click, or Alt+Insert) to create a Java class. Name it ToolboxCheck. The IDE creates ToolboxCheck.java and it opens in the editor. The file name matches the class name, exactly as lesson 1 required. A new class file usually opens with the class declaration already written. Complete it:

public class ToolboxCheck {
    public static void main(String[] args) {
        System.out.println("Hello from the IDE.");
        System.out.println("Java version: " + System.getProperty("java.version"));
        System.out.println("Java home: " + System.getProperty("java.home"));
    }
}

main is the starting point: the Java launcher begins here. The System.getProperty calls ask the running JVM about itself. java.version is the version of the Java that runs the program, and java.home is the folder of the installation that runs it. These are standard system properties, so the program shows you which JDK the IDE actually used.

To run it, click the green arrow (Run) in the editor margin next to the class or the main method, and choose to run ToolboxCheck.main(). JetBrains' tutorial describes this gutter arrow. Many default keymaps also have a run shortcut, but shortcuts can differ, so use the arrow if you are unsure.

Reading the output: the Run window

A Run tool window opens at the bottom of the screen. JetBrains' tutorial says the program's output appears there, and that the last line reports an exit code, where 0 means the program finished successfully. For ToolboxCheck you see the three lines, and then something like Process finished with exit code 0.

If you close the window by accident, the documentation lists the shortcut Alt+4 to bring it back, and it appears only after you have run something. The same page lists Alt+1 for the Project window and Alt+F12 for the Terminal window, which is a command line inside the IDE that starts in the project folder.

A tour of the window

Try breaking the program on purpose. Delete the final semicolon of one println line. The IDE underlines the problem, usually in red, and the message tells you what it expected. Fix it and run again. This is the error highlighting at work, and you have already saved yourself a compile cycle.

Closing a project, and coming back

Close a project through the File menu, using the Close Project item. In JetBrains' documentation I read, the Welcome screen is what you see after the last project closes. I could not open the page that describes the Close Project menu item itself, so check for it in your version's File menu, or use Find Action (see the Help menu for its shortcut) and type "close project". After closing, the Welcome screen lists your recent projects, so you can reopen hello-ide with one click.

Closing is not the same as quitting the application. Closing the project returns you to the Welcome screen, while quitting the application closes the whole IDE.

The IDE has its own JDK setting

One idea matters for later lessons. IntelliJ keeps a project JDK setting inside each project. It uses that JDK to compile and run, whatever your terminal's PATH says. So you can be in an odd state, such as a terminal that says "command not found" while the IDE works fine, or a terminal using a different Java version than the IDE. That is why ToolboxCheck prints java.home: it tells you the truth about the IDE's choice. To see or change the project JDK, look for the project settings in the File menu (often called Project Structure). Menu names can differ by version.