Determine java class hierarchies programmatically

ClassHierarchy.java

import java.io.File;
import java.util.Set;

import javax.annotation.processing.*;
import javax.lang.model.*;
import javax.lang.model.element.*;
import javax.tools.*;

import com.sun.source.tree.*;
import com.sun.source.util.*;

import static java.util.Collections.singleton;

public class ClassHierarchy {

    public static void main(String... args) throws Exception {
        File search_dir = new File(args[0]);

        JavaCompiler jc = ToolProvider.getSystemJavaCompiler();
        StandardJavaFileManager jfm = jc.getStandardFileManager(null, null, null);
        jfm.setLocation(StandardLocation.SOURCE_PATH, singleton(search_dir.getAbsoluteFile()));

        Iterable<JavaFileObject> sources = jfm.list(StandardLocation.SOURCE_PATH,
                                                    "",
                                                    singleton(JavaFileObject.Kind.SOURCE),
                                                    true);

        JavaCompiler.CompilationTask task = jc.getTask(null, jfm, null, null, null, sources);
        task.setProcessors(singleton(new CodeProcessor()));

        task.call();
    }
}

@SupportedSourceVersion(SourceVersion.RELEASE_8)
@SupportedAnnotationTypes("*")
class CodeProcessor extends AbstractProcessor {
    private final ASTVisitor visitor = new ASTVisitor();
    private Trees ast;

    @Override
    public void init(ProcessingEnvironment pe) {
        super.init(pe);
        ast = Trees.instance(pe);
    }

    @Override
    public boolean process(Set<? extends TypeElement> _annotations, RoundEnvironment env) {
        for (Element e: env.getRootElements()) {
            Tree node = ast.getTree(e);
            node.accept(visitor, null);
        }

        return true;
    }
}

class ASTVisitor extends SimpleTreeVisitor<Object, Trees> {
    @Override
    public Object visitClass(ClassTree node, Trees ast) {
        System.out.println(node.getSimpleName());
        System.out.println("\textends: " + node.getExtendsClause());
        System.out.println("\timpls: " + node.getImplementsClause());
        return super.visitClass(node, ast);
    }
}

gistfile1.md

Given you have the access to the source files, this should work. And apparently, I can't take full credit. CollectionGenericsTypeExctractor.java helps a lot. And man, the API is ugly!

output.md

$ javac -version
javac 1.8.0_112

$ javac -cp path/to/tools.jar:. ClassHierarchy.java
$ java -cp path/to/tools.jar:. ClassHierarchy .
ClassHierarchy
        extends: null
        impls:
CodeProcessor
        extends: AbstractProcessor
        impls:
ASTVisitor
        extends: SimpleTreeVisitor<Object, Trees>
        impls: