The key steps in configuring a Java debugging environment on VSCode include: 1. Install JDK and verify; 2. Install Java Extension Pack and Debugger for Java plug-in; 3. Create and configure the launch.json file, specify mainClass and projectName; 4. Set up the correct project structure to ensure the source code path and compilation output are correct; 5. Use debugging techniques such as Watch, F8/F10/F11 shortcut keys and methods to deal with common problems such as class not found or JVM attachment failures.
Configuring a Java debugging environment is actually not difficult on VSCode, but it may be a bit trampled for beginners. The key is to match several core components: JDK, plug-in, launch.json file and project structure. As long as these parts are fine, debugging can run smoothly.
Install the JDK and VSCode plug-in
First of all, you have to confirm that you have installed JDK locally. It is recommended to use OpenJDK or Adoptium (formerly called AdoptOpenJDK). You can use the terminal to enter java -version and javac -version to verify whether the installation is successful.
Then open VSCode and install the following two plugins:
- Java Extension Pack : This is the basic set of Java development, including language support, project management, etc.
- Debugger for Java : This plugin is really used for debugging, and it will automatically generate some configuration files for you.
After these two plug-ins are installed, VSCode will have basic Java development and debugging capabilities.
Create launch.json configuration file
If you are debugging a Java project for the first time, VSCode may prompt you to create a launch.json file when clicking on the "Run and Debug" sidebar. If it does not automatically pop up, you can manually click "Create launch.json file" and select "Launch Current File" or "Launch Program" in Java.
The core function of this file is to specify the startup class and JVM parameters. For example, you can write this:
{
"type": "java",
"request": "launch",
"name": "Debug (Launch) - Current File",
"mainClass": "com.example.Main",
"projectName": "your-project-name"
}Note two points:
- mainClass To write the full class name, including the package name.
- If you are a multi-module project, it is best to fill in projectName as well to avoid not finding the class.
Set up the correct project structure
VSCode has certain requirements for the structure of Java projects. Generally speaking, the source code should be placed in the src/main/java directory, and there should be a .classpath file or Maven/Gradle configuration file. If you are using a normal folder instead of a Maven/Gradle project, you may need to manually set the compiled output path.
FAQ:
- Class not found: Check whether build path and output folder are correct.
- An error "Source not found" was reported at startup: It may be that the class where the breakpoint is located was not compiled or loaded correctly.
The recommended approach is:
- Initialize the project structure using Maven or Gradle.
- Make sure that the compiled
.classfile is underbinortarget/classes.
Common debugging operation skills
When debugging Java, in addition to adding breakpoints, there are some tips to improve efficiency:
- Right-click on the variable to select "Watch" to view the value changes in real time.
- Press F8 to quickly skip the current breakpoint, F10 is the stepping function, and F11 is the execution line by line.
- If the debugging is stuck, you can click the "Pause" button to see the current thread status.
Also, sometimes you will encounter "cannot attach to JVM", and you can try:
- Clean up the cache files in the .vscode directory.
- Restart VSCode and reload the Java plug-in (Ctrl Shift P enter "Reload Window").
Basically that's it. The whole process is not complicated, but it is easy to cause problems in details, especially when the path and class names are written incorrectly. As long as you take it step by step, it can usually be done.
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