Setup

There are three places to write Scratch for Java. The code is the same in all of them, so you can start in one and move on to another later.

Saving your work

• In the browser your code is kept only in this browser on this computer. Download your project before you switch computers or clear the browser, and load it again on the other side. Studio can open these downloads too.
• In Studio press Ctrl+S (Cmd+S on a Mac). Your project is an ordinary folder of Java files and pictures. Keep that folder together when you copy it.
• In BlueJ or VS Code your project is a folder as well. Copy the whole folder, including the +libs folder with the library inside.

From the browser to your own computer

The examples in the browser start with a void main() above the classes:

void main() {
  Window myWindow = new Window(480, 360);
  myWindow.setStage(new MyStage());
}

That is a complete Java program in Java 25 and newer, and Studio runs it as it is. In BlueJ and elsewhere, put the same lines into a main method of your stage, and in BlueJ run it by right-clicking MyStage and choosing void main(String[] args):

import org.openpatch.scratch.*;
 
public class MyStage extends Stage {
  public MyStage() {
    Sprite bunny = new Sprite();
    bunny.addCostume("bunny1_stand");
    this.add(bunny);
  }
 
  public static void main(String[] args) {
    Window myWindow = new Window(480, 360);
    myWindow.setStage(new MyStage());
  }
}

Your own Java files also need the import org.openpatch.scratch.*; at the top. The browser adds it for you.

Studio

Create a project from the start screen and run the stage with ▶. Studio has a stage designer, costume and sound tools, a browser for the built-in pictures and sounds, and a debugger. You can also import the finished project of each tutorial through the Project menu.

VS Code

First make sure you have the Java Extension Pack installed. You can find it in the Extensions view by searching for redhat.java.

Then download the Scratch for Java JAR.

Afterward, you need to add the jar to your project. You can do this by adding the following to your settings.json:

"java.project.referencedLibraries": [
    "path/to/scratch4j.jar"
]

If you want to be compatible with BlueJ you should use a "+libs" folder in your project, add the jar there and then add the following to your settings.json:

"java.project.referencedLibraries": [
    "+libs/*.jar"
]

BlueJ

You can install this library via three ways in BlueJ.

First, download the Scratch for Java JAR, or start from the BlueJ starter project there, which already has it in its +libs folder.

Project-by-project

Create a directory called "+libs" inside your project. Copy the Scratch for Java jar into the "+libs" folder. Restart BlueJ - done. Scratch for Java will now be available for this project.

User Preferences

Open the "Preferences" dialogue and select the "Libraries" tab. Then add the location where the Scratch for Java jar is located. Restart BlueJ - done. Scratch for Java will now be available in all of your projects that you open.

System Wide

You need to locate the "userlib" folder, found at <bluej-dir>/lib/userlib. Place the Scratch for Java jar into this folder. Restart BlueJ - done. Scratch for Java will now be available in all projects for all users.

If you have installed BlueJ via the installer you probably find the "userlib" folder here:

• Windows: C:\Program Files\BlueJ\lib\userlib
• MacOS: /Application/BlueJ/BlueJ.app/Resources/java/userlib
• Linux: /usr/share/bluej/userlib/

Standalone

Add the JAR to the classpath.

Maven

You can also use Scratch for Java via Maven. Just add the following dependency to your pom.xml:

<dependency>
    <groupId>org.openpatch</groupId>
    <artifactId>scratch</artifactId>
    <version>6.5.0</version>
</dependency>

We have also prepared a starter for you: Maven Starter