Java in VS Code

The Java support in VS Code is provided through extensions and optimized for lightweight Java projects with a simple, modern workflow. Popular extensions in the Marketplace provide project support, code completion, linting, debugging, code formatting, snippets, and more.

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Install Java Extensions

VS Code is a fast editor and ships with only the basic features. Add Java language support to VS Code by installing the popular Java extensions.

  1. In Visual Studio Code, go to the Extensions view (⇧⌘X (Windows, Linux Ctrl+Shift+X)).
  2. Filter the extensions list by typing "java".

To help set up Java on VS Code, there is a Java Extension Pack which contains two popular extensions:

  1. Language Support for Java(TM) by Red Hat
  2. Java Debugger for Visual Studio Code

Install the Java Extension Pack

This document describes the features included in the Java Extension Pack.

Java Project Support

Maven, Eclipse and Gradle Java project are supported through Language Support for Java(TM) by Red Hat, by utilizing M2Eclipse which provides Maven support and Buildship which provides Gradle support through the Eclipse JDT Language Server.

Please note that Gradle-based Android projects are not supported.

Editing and Navigating Code

Java Code Editing

Linting

A linter is a tool that provides warnings for suspicious looking code. Language Support for Java(TM) by Red Hat provides this feature to report parsing and compilation errors as you type, so you can fix them inside VS Code.

Intellisense

VS Code also supports code completion and Intellisense for Java through Language Support for Java(TM) by Red Hat. Intellisense is a general term for a number of features, including intelligent code completion (in-context method and variable suggestions) across all your files and for built-in and thirty-party modules.

Search for symbols

You can search for symbols in the current file or workspace to navigate your code more quickly.

To search for a symbol in the current file, use Quick Open (⌘P (Windows, Linux Ctrl+P)) then enter the '@' command, then enter the name of the symbol you're looking for. A list of potential matches will appear and be filtered as you type. Choose from the list of matches to navigate to its location.

To search for a symbol in the current workspace, start by pressing ⌘T (Windows, Linux Ctrl+T), then enter the name of the symbol. A list of potential matches will appear as before. If you choose a match that was found in a file that's not already open, the file will be opened before navigating to the match's location. Alternatively, you can also use Quick Open (⌘P (Windows, Linux Ctrl+P)) then enter the '#' command to search the current workspace. ⌘T (Windows, Linux Ctrl+T) is just the shortcut for the '#' commands, respectively, so everything works the same.

Peek Definition

You can take a quick look at how a symbol was defined by using the Peek Definition feature. This feature displays a few lines of code near the definition inside a peek window so you can take a look without navigating away from your current location.

To peek at a symbol's definition, place your cursor on the symbol anywhere it's used in your source code and then press ⌥F12 (Windows Alt+F12, Linux Ctrl+Shift+F10). Alternatively, you can choose Peek Definition from the context menu (right-click, then choose Peek Definition).

Go to Definition

You can also quickly navigate to where a symbol is defined by using the Go to Definition feature.

To go to a symbol's definition, place your cursor on the symbol anywhere its used in your code and then press F12. Alternatively, you can choose Go to Definition from the context menu (right-click, then choose Go to Definition). When there's only one definition of the symbol, you'll navigate directly to its location, otherwise the competing definitions are displayed in a peek window as described in the previous section and you have to choose the definition that you want to go to.

Other code editing features include:

  • Code formatting
  • Code snippets
  • Code outline
  • Code lens (references)
  • Javadoc hovers
  • Rename
  • Highlights

Debugging

Java Debugger for Visual Studio Code is a lightweight Java Debugger based on Java Debug Server. It works with Language Support for Java by Red Hat to allow users debugging Java code using Visual Studio Code (VS Code).

The Java Debugger supports following features:

  • Launch/Attach - You can either launch the Java project within VS Code or attach to any running JVM process in debug mode, locally or remotely.
  • Breakpoints - Conditional breakpoints by Hit Count is supported and can easily be set using the inline breakpoint settings window. This allows you to conveniently add conditional breakpoints to your code, directly in the source viewer, without requiring a modal window. Break on exceptions is also supported.
  • Control flow - Including Pause, Continue F5, Step over F10, Step into F11, Step out Shift+F11
  • Data inspection - When you're stopped at a breakpoint, the debugger has access to the variable names and values that are currently stored in memory. Inspect/Watch/Set Variables are supported.
  • Diagnostics - The CALL STACK panel shows the call stack of your program and allows you to navigate through the call path of each captured allocation. Multi-threaded debugging is supported by parallel stacks.
  • Debug Console - The Debug Console lets you see information from both stdout and stderr.

Debugging Features

You can launch the debugger following steps below:

  1. Switch to the Debug view (⇧⌘D (Windows, Linux Ctrl+Shift+D)).
  2. Open launch.json to add a debug configuration for Java
  3. Fill in the mainClass for Launch setting or hostName and port for Attach.
  4. Click Start button or press F5 to start debugging.

Debugging Java Application

Next Steps

Read on to find out about:

  • Basic Editing - Learn about the powerful VS Code editor.
  • Code Navigation - Move quickly through your source code.
  • Tasks - use tasks to build your project and more
  • Debugging - find out how to use the debugger with your project