在Jung中更改（重命名）顶点标签

Question

Is there a way to change vertex label?
For example, in my JUNG graph app, I have two vertexes A and B,
how can I rename just an special vertex label?

Now i use this method but it changes all vertex name.

vv.getRenderContext().setVertexLabelTransformer(new Transformer<String,String>() {
 @Override
 public String transform(String i) {
 return "test";
 }
 });

Thanks for your help.

Answer 1

There are a few things to consider here.

A Transformer<S, T> is just a functional interface [1] for a class that, given an object of type S , returns an object of type T . The behavior of the transform method can be anything you like that returns an object of type T .

Because it's a functional interface, you can make the syntax a little bit clearer (assuming you're using Java 8+) with a lambda expression.

So a naive way to rename just "A" to "B" (using Java 8 lambdas) could be the following:

vv.getRenderContext().setVertexLabelTransformer(i -> {
      return i.equals("A")
          ? "B"
          : i;  
    }

However, this is a terrible solution because it hardcodes the mapping and doesn't allow you to change the name of other nodes, or to change the names again (say, in response to user input), without further code changes.

A more robust way to do this would be to have a Map<S, T> called labels that your function could reference:

vv.getRenderContext().setVertexLabelTransformer(i -> labels.get(i));

This way you can update labels as much as you like.

You may also want to consider whether your nodes should be represented by String objects, or whether they should be objects that contain a String field that you can use as a label. I generally find that it's a good idea to decouple the node object from its label (among other things, that allows the labels to be non-unique, which the node objects can't be).

[1] And in fact version 3.0 of JUNG will just use java.util.Function in place of Transformer .