{"title":"Setting Up Environment","description":"","content":"Before you write a single line of Java, your machine needs a JDK installed and an editor that understands it. By the end of this lesson, `java -version` will print a real version string in your terminal, and you'll have an IDE open and ready.\n\nThis chapter only covers setup. Here, you just install one.\n\n---\n\n# The Setup Flow\n\nThe process is short. Pick a JDK, install it, set up `JAVA_HOME` and `PATH` if the installer didn't, verify it works, then install an IDE.\n\n\n```mermaid\nflowchart LR\n A[Pick a JDK
distribution] --> B[Install on
your OS]\n B --> C[Set JAVA_HOME
and PATH]\n C --> D[Verify with
java -version]\n D --> E[Install an IDE]\n E --> F[Ready to code]\n\n classDef start fill:#00ceff,stroke:#000,color:#000\n classDef step fill:#ffa94d,stroke:#000,color:#000\n classDef verify fill:#38d9a9,stroke:#000,color:#000\n classDef done fill:#69db7c,stroke:#000,color:#000\n\n class A start\n class B,C,E step\n class D verify\n class F done\n```\n\n\nTake the steps in order and don't skip the verification one. A common cause of \"Java doesn't work\" is a terminal that was opened before the installer finished writing the `PATH`.\n\n---\n\n# Pick a JDK Distribution\n\nA JDK is the compiler, runtime, and standard library together. Several companies ship their own builds of it, all based on the same upstream open-source project called OpenJDK. They behave the same for almost everything a learner will do. The choice mostly comes down to license terms and who's supplying the binaries.\n\nThe safe default is **Eclipse Temurin** from the Adoptium project. It's free, widely used in production, and ships builds for macOS, Windows, and Linux on both Intel and ARM.\n\nThe common alternatives:\n\n\n| Distribution | Vendor | License | Notes |\n|---|---|---|---|\n| **Eclipse Temurin** | Adoptium (Eclipse Foundation) | GPL with Classpath Exception | Recommended default. Replaced AdoptOpenJDK in 2021. |\n| Oracle JDK | Oracle | Oracle NFTC for current LTS | Free for development and most production use under the NFTC license. |\n| Amazon Corretto | Amazon | GPL with Classpath Exception | Used heavily inside AWS, free for all use. |\n| Azul Zulu | Azul Systems | GPL with Classpath Exception | Free Community edition, lots of older-version builds. |\n\n\nPick Temurin unless your team already standardized on one of the others.\n\n---\n\n# Pick a Java Version\n\nJava releases a new version every six months, but most of those are short-lived. Every few years, one release gets the **LTS** label, which stands for Long-Term Support. LTS versions get security patches and bug fixes for years, which is why companies build on them.\n\nUse **Java 21 or Java 25**, the two newest LTS releases. Java 17 is also a fine choice if a project you're working with hasn't moved off it yet. Avoid non-LTS versions like 22, 23, or 24 for learning, because tutorials, libraries, and Stack Overflow answers all tend to assume an LTS.\n\nWhy does this matter? Two reasons. First, some language features only exist in certain versions. Pattern matching for switch landed in Java 21. Records arrived in Java 16. If you pick Java 11 because it was on an old machine, half of the modern Java syntax in this course won't compile. Second, sample code from a blog post written this year almost certainly expects 21, 25, or 17.\n\n---\n\n# Install on macOS\n\nOn macOS you have two reasonable paths: download the official Temurin installer, or use Homebrew.\n\n**Option 1: the `.pkg` installer.** Visit `https://adoptium.net/`, pick the Temurin 21 (LTS) build for macOS, and choose the right architecture. If your Mac has an Apple Silicon chip (M1, M2, M3, M4), pick the `aarch64` package. If it's an older Intel Mac, pick `x64`. Download the `.pkg`, double-click it, and follow the installer. It places the JDK under `/Library/Java/JavaVirtualMachines/`.\n\n**Option 2: Homebrew.** If you already use Homebrew, this is a one-liner:\n\n\n```shell\nbrew install --cask temurin@21\n```\n\n\nAfter either path finishes, list the JDKs macOS knows about:\n\n\n```shell\n/usr/libexec/java_home -V\n```\n\n\nThat last path is what `JAVA_HOME` should point to.\n\nIf you ever have several JDKs installed at once, you can ask `java_home` for a specific version:\n\n\n```shell\n/usr/libexec/java_home -v 21\n```\n\n\nThe path it prints is the one to use.\n\n---\n\n# Install on Windows\n\nOn Windows, download the Temurin 21 `.msi` installer from `https://adoptium.net/`. Pick the `x64` build unless you're on an ARM Windows machine, in which case pick the ARM build.\n\nRun the installer. On one of the screens, the installer asks whether to set `JAVA_HOME` and add `java` to `PATH`. Check both boxes. This single click saves a lot of trouble.\n\nAfter the installer finishes, **close any open terminal or PowerShell windows**, then open a new one. Environment variables set by an installer aren't picked up by terminals that were already running. This is the most common reason a fresh install seems broken.\n\nIn the new PowerShell window:\n\n\n```shell\njava -version\njavac -version\necho $env:JAVA_HOME\n```\n\n\nIf all three print something sensible, you're done. If they don't, jump to the Common Issues section at the end.\n\n---\n\n# Install on Linux\n\nOn Linux, your package manager is usually the simplest path.\n\n**Debian or Ubuntu:**\n\n\n```shell\nsudo apt update\nsudo apt install openjdk-21-jdk\n```\n\n\n**Fedora, RHEL, or CentOS Stream:**\n\n\n```shell\nsudo dnf install java-21-openjdk-devel\n```\n\n\nThe `-devel` package matters. The non-devel package only installs the JRE, which can run Java code but can't compile it. Without it, `javac` won't exist.\n\nIf you'd rather have multiple Java versions side by side (useful when working across projects that pin different versions), use **SDKMAN**:\n\n\n```shell\ncurl -s \"https://get.sdkman.io\" | bash\nsource \"$HOME/.sdkman/bin/sdkman-init.sh\"\nsdk install java 21.0.5-tem\n```\n\n\nThe `-tem` suffix tells SDKMAN to grab Temurin. SDKMAN handles `JAVA_HOME` and `PATH` for you and lets you switch versions with `sdk use java `.\n\n---\n\n# Set `JAVA_HOME` and `PATH`\n\n`JAVA_HOME` is an environment variable that points to the root of your JDK install. Lots of tools (build tools like Maven and Gradle, IDEs, scripts) read it to find Java. `PATH` is the list of directories your shell searches when you type a command, and it needs to include the JDK's `bin` directory so that typing `java` or `javac` works from anywhere.\n\nOn Windows, if you checked the boxes in the installer, both are already set. On macOS and Linux, you'll usually want to set them yourself in your shell profile.\n\n**macOS (zsh, the default since Catalina).** Edit `~/.zshrc`:\n\n\n```shell\nexport JAVA_HOME=$(/usr/libexec/java_home -v 21)\nexport PATH=$JAVA_HOME/bin:$PATH\n```\n\n\nThe `$(/usr/libexec/java_home -v 21)` part runs that command and substitutes its output. That way, you don't have to hardcode the JDK path. Reload the shell with `source ~/.zshrc` or just open a new terminal tab.\n\n**Linux (bash).** Edit `~/.bashrc` (or `~/.profile` on some setups):\n\n\n```shell\nexport JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64\nexport PATH=$JAVA_HOME/bin:$PATH\n```\n\n\nThe exact path depends on your distribution. On Debian/Ubuntu it's usually under `/usr/lib/jvm/`. Run `ls /usr/lib/jvm/` to confirm the directory name and copy that into the export. After editing, run `source ~/.bashrc`.\n\n**Windows (PowerShell, persistent).** From an elevated PowerShell prompt:\n\n\n```shell\n[Environment]::SetEnvironmentVariable(\"JAVA_HOME\", \"C:\\Program Files\\Eclipse Adoptium\\jdk-21\", \"User\")\n$existingPath = [Environment]::GetEnvironmentVariable(\"Path\", \"User\")\n[Environment]::SetEnvironmentVariable(\"Path\", \"$existingPath;%JAVA_HOME%\\bin\", \"User\")\n```\n\n\nReplace the path with the actual install location if yours is different. Close the PowerShell window after running these and open a fresh one for the changes to take effect.\n\n---\n\n# Verify the Install\n\nThree commands tell you whether everything is wired up correctly.\n\n\n```shell\njava -version\n```\n\n\nThe version number and the word \"Temurin\" are the markers to look for. Corretto and Zulu installs print those names instead. The middle line shows the runtime; the third line shows the VM.\n\n\n```shell\njavac -version\n```\n\n\n`javac` is the compiler. It's part of the JDK, not the JRE. If `java` works but `javac` says \"command not found\", you installed the JRE by mistake. Install the JDK package and try again.\n\n\n```shell\necho $JAVA_HOME\n```\n\n\n(On Windows, run `echo $env:JAVA_HOME` in PowerShell.) The exact path varies, but it should end somewhere inside a directory whose name has `21` in it.\n\nIf the version that `java -version` prints doesn't match what `javac -version` prints, your `PATH` is picking up a `java` from one install and a `javac` from another. We'll fix that in the Common Issues section.\n\n---\n\n# Pick an IDE\n\nA plain text editor plus `javac` and `java` is enough to compile and run code. But for any project beyond a one-file demo, an IDE pays for itself within the first hour. It catches errors as you type, autocompletes class and method names, jumps you to definitions, and handles the build for you.\n\nThree IDEs dominate Java work:\n\n\n| Criteria | IntelliJ IDEA Community | VS Code + Extension Pack for Java | Eclipse |\n|---|---|---|---|\n| Cost | Free | Free | Free |\n| Best for | Beginners and most Java work | Polyglot devs already on VS Code | Legacy enterprise codebases |\n| Strengths | Best Java tooling, smart refactoring, intuitive UI | Lightweight, great if you use VS Code for other languages | Long history, used in big enterprise shops |\n| Weaknesses | Uses more memory than VS Code | Java support is good but not as deep as IntelliJ | UI feels dated, steeper learning curve |\n| Recommended for this course? | Yes | Yes, as a lighter alternative | Only if you already know it |\n\n\nIf you're new to Java, install **IntelliJ IDEA Community Edition**. The \"Community\" part is important; it's the free version. The paid Ultimate edition adds features for Spring, JavaScript, and database tooling, but you don't need any of that yet.\n\n### IntelliJ IDEA Community\n\nDownload it from `https://www.jetbrains.com/idea/download/`. Scroll past the Ultimate section to find Community. Install and launch.\n\nOn first launch, IntelliJ asks if you want to create a new project. Click **New Project**. Set the name to `MyShop`. For the JDK dropdown, IntelliJ should auto-detect the Temurin 21 install you just made. If it doesn't, click **Add JDK** and point it at the path that `JAVA_HOME` holds. Leave the build system as IntelliJ (instead of Maven or Gradle) for now. Click **Create**.\n\nIntelliJ opens the project. A `src` folder appears on the left. That's where Java source files go.\n\n### VS Code with Extension Pack for Java\n\nIf you already use VS Code, install Microsoft's **Extension Pack for Java**. Open VS Code, hit the Extensions icon, search for \"Extension Pack for Java\", and install. It bundles six extensions, including the language server, debugger, and test runner.\n\nVS Code in Java mode works differently from IntelliJ. There's no \"create new project\" wizard for plain Java. Instead, you make an empty folder named `MyShop` somewhere on disk, open it in VS Code (**File** > **Open Folder**), and start adding `.java` files inside it. The extension pack picks them up automatically and sets up everything in the background.\n\nYou can confirm Java is wired up by opening the Command Palette (Cmd+Shift+P on macOS, Ctrl+Shift+P elsewhere) and running `Java: Configure Java Runtime`. It shows the JDKs it detected.\n\n### Eclipse\n\nEclipse is still around, and plenty of older codebases assume it. If you have a specific reason to use it (a job that requires it, a course that uses it, or familiarity), download the Eclipse IDE for Java Developers from `https://www.eclipse.org/downloads/`. For most readers of this course, IntelliJ Community is the better starting point.\n\n---\n\n# Common Issues and Fixes\n\nEven with everything done right, three problems show up often. Knowing how to recognize them saves time.\n\n**Problem 1: `command not found: java` after install.**\n\nYou ran the installer, but a fresh `java -version` says the command doesn't exist.\n\nTwo causes. First, the terminal window was open before the installer added `java` to `PATH`. Close it and open a new one. Second, on macOS and Linux, the installer might not edit your shell profile. Open `~/.zshrc` (or `~/.bashrc`) and confirm there's an `export PATH=$JAVA_HOME/bin:$PATH` line. If not, add it and run `source ~/.zshrc`.\n\nOn Windows, this often means the installer didn't get permission to update `PATH`. Reinstall the `.msi` and make sure to check the \"Set JAVA_HOME\" and \"Add to PATH\" boxes.\n\n**Problem 2: `java -version` shows one version, `javac -version` shows another.**\n\nExample:\n\n\n```shell\n$ java -version\nopenjdk version \"1.8.0_392\"\n$ javac -version\njavac 21.0.5\n```\n\n\nThis means your machine has multiple Java installs and `PATH` points to one for `java` and another for `javac`. Run `which java` and `which javac` (or `where java` on Windows) to see the actual paths. Whichever one is wrong, fix it by reordering `PATH` so that the correct JDK's `bin` directory comes first.\n\nOn macOS, the cleanest fix is to anchor `JAVA_HOME` to a specific version:\n\n\n```shell\nexport JAVA_HOME=$(/usr/libexec/java_home -v 21)\nexport PATH=$JAVA_HOME/bin:$PATH\n```\n\n\nOn Linux, the system-wide way is `update-alternatives`:\n\n\n```shell\nsudo update-alternatives --config java\nsudo update-alternatives --config javac\n```\n\n\nBoth commands show a numbered list of installed Javas. Pick the one matching your target version.\n\n**Problem 3: IDE can't find a JDK.**\n\nYou opened IntelliJ or VS Code, and it complains that no JDK is configured. The OS knows about your JDK (`java -version` works in the terminal), but the IDE doesn't.\n\nIn IntelliJ: **File** > **Project Structure** > **Project** > **SDK**. Click **Add SDK** > **JDK** and point it at the path stored in `JAVA_HOME`. On macOS, that's typically something like `/Library/Java/JavaVirtualMachines/temurin-21.jdk/Contents/Home`. Find yours by running `echo $JAVA_HOME` in the terminal.\n\nIn VS Code: run `Java: Configure Java Runtime` from the Command Palette. If your JDK isn't listed, click the install link or set the `java.jdt.ls.java.home` setting to the JDK path manually.","pageType":"java"}

Setting Up Environment

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