Var decl

package com.unipr;

import java.io.IOException;
import java.util.ArrayList;

import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

import com.sun.source.util.TreePath;
import com.sun.source.util.Trees;
import com.sun.tools.javac.api.JavacTaskImpl;
import com.sun.tools.javac.code.Kinds;
import com.sun.tools.javac.main.OptionName;
import com.sun.tools.javac.model.JavacElements;
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.tree.JCTree.JCFieldAccess;
import com.sun.tools.javac.tree.JCTree.JCIdent;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.util.List;

/**
 * singletest/A.java is:
 *
 * public class A {
 *   private static final int j = 0;
 *   private int f() {
 *     int x = 1;
 *     return B.i + j + x;
 *   }
 * }
 *
 * singletest/B.java is:
 *
 * public class B {
 *   public static final int i = 0;
 * }
 *
 *
 * Output:
 *
 * decl for i:
 * public static final int i = 0
 *
 * decl for j:
 * private static final int j = 0
 *
 * decl for x:
 * int x = 1
 */
public class TreeVisitor extends TreeScanner {
  private Trees trees;
  private TreePath path;
  private JavacElements elements;

  public TreeVisitor(JavacTaskImpl task) {
    trees = Trees.instance(task);
    elements = JavacElements.instance(task.getContext());
  }

  public void scan(JCTree tree) {
    if (tree != null) {
      TreePath prev = path;
      path = new TreePath(path, tree);
      try {
        tree.accept(this);
      } finally {
        path = prev;
      }
    }
  }

  @Override
  public void visitIdent(JCIdent tree) {
    if(tree.sym != null && tree.sym.kind == Kinds.VAR) {
      JCTree declTree = elements.getTree(tree.sym);
      System.out.println("decl for " + tree.sym + ":\n" + (declTree == null ? "<no_decl??>" : declTree) + "\n");
    }
    super.visitIdent(tree);
  }

  @Override
  public void visitSelect(JCFieldAccess tree) {
    if (tree.sym != null && tree.sym.kind == Kinds.VAR) {
      JCTree declTree = (JCTree) trees.getTree(tree.sym);
      System.out.println("decl for " + tree.sym + ":\n" + declTree + "\n");
    }
    super.visitSelect(tree);
  }

  @SuppressWarnings("unchecked")
  public static void main(String[] args) throws IOException {
    JavaCompiler tool = ToolProvider.getSystemJavaCompiler();
    StandardJavaFileManager fm = tool.getStandardFileManager(null, null, null);
    Iterable<? extends JavaFileObject> files = fm.getJavaFileObjects("./singletest/A.java");
    java.util.List<String> opts = new ArrayList<String>();
    opts.add(OptionName.SOURCEPATH.optionName);
    opts.add("./singletest");
    JavacTaskImpl task = (JavacTaskImpl)tool.getTask(null, fm, null, opts, null, files); // cast to JavacTaskImpl so I can get the context later
    List<JCCompilationUnit> units = (List<JCCompilationUnit>) task.parse();
    task.analyze();
    new TreeVisitor(task).scan(units.head);
  }
}