This is a Java library for working with Nassi-Shneiderman diagrams (structograms).

It offers the following functionality:

• Construct elements through code
  • All standard block types supported
• Read structograms from files
  • Currently only support for the Structorizer format, but easy to add your own
• Render structograms as images
  • Basic layouting, dynamic size calculation
  • High amount of abstraction through RenderAdapter (AWT adapter included; support for custom adapters for other targets, e.g. Android)

The following code reads a structogram stored in Structorizer's XML format.

NSDReader reader = new StructorizerReader();

NSDRoot root;

File file = new File("/path/to/file.nsd");
try (FileInputStream in = new FileInputStream(file)) {
    root = reader.read(in);
} catch (NSDReaderException | IOException e) {
    e.printStackTrace();
}

// do something with `root`

Feel free to submit a PR or open an issue if you require support for other formats. The custom reader should implement the NSDReader interface.

To render a structogram (or part of one), the following steps need to be done:

1. Convert the element into a RenderPart (do this for the root element).
2. Layout the render part.
3. Render the actual image.

The following example uses the AwtRenderer for rendering to a BufferedImage, but you can easily substitute a custom renderer instead.

AwtRenderer renderer = new AwtRenderer();

// 1. convert (`diagram` is an instance of `NSDRoot`)
RenderPart part = diagram.toRenderPart();

// 2. layout
part.layout(renderer.createContext());
// optional: get the resulting size
// Size s = part.getSize();

// 3. render
BufferedImage img = renderer.render(part);

Constructing a structogram with code is as simple as invoking a few constructors.

NSDRoot diagram = new NSDRoot("When start clicked");

NSDDecision dec = new NSDDecision("(pick random 1 to 10) = 1");
{
    dec.getThen().addChild(new NSDInstruction("say \"You're lucky!\""));
    dec.getElse().addChild(new NSDInstruction("say \"Not so lucky.\""));
}
diagram.addChild(dec);

NSDForever forever = new NSDForever(Arrays.asList(
    new NSDInstruction("wait 1 secs")
));
diagram.addChild(forever);

// etc

The base class for every element is nsdlib.elements.NSDElement. Elements that contain other elements extend its subclass nsdlib.elements.NSDContainer.