package com.karateca.jstoolbox.generatemethod;

import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.editor.Document;
import com.intellij.openapi.project.Project;
import com.intellij.util.EventDispatcher;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.util.ArrayList;
import java.util.List;

/**
 * @author Andres Dominguez
 */
class ParentNamespaceFinder {

  private final Document document;
  private final EventDispatcher<ChangeListener> myEventDispatcher =
      EventDispatcher.create(ChangeListener.class);
  private final Project project;
  private List<Function> functionNames;
  private String currentNamespace;
  private String parentNamespace;

  List<Function> getFunctionNames() {
    return functionNames;
  }

  String getCurrentNamespace() {
    return currentNamespace;
  }

  String getParentNamespace() {
    return parentNamespace;
  }

  public ParentNamespaceFinder(Document document, Project project) {
    this.document = document;
    this.project = project;
  }

  public void findParentClass() {
    ApplicationManager.getApplication().runReadAction(new Runnable() {
      @Override
      public void run() {
        functionNames = new ArrayList<Function>();

        HierarchyFinder hierarchyFinder = new HierarchyFinder(project, document);
        HierarchyResults parents = hierarchyFinder.findParents();

        for (Document doc : parents.getHierarchy()) {
          ClassFinder finder = new ClassFinder(doc);
          functionNames.addAll(finder.getSortedMethods());
        }

        currentNamespace = parents.getCurrentClass();
        parentNamespace = parents.getParentClass();
        functionNames = getFunctionNames();

        broadcastReady();
      }
    });
  }

  private void broadcastReady() {
    myEventDispatcher.getMulticaster().stateChanged(new ChangeEvent("ParentNamespaceFound"));
  }

  /**
   * Register for change events.
   *
   * @param changeListener The listener to be added.
   */
  public void addResultsReadyListener(ChangeListener changeListener) {
    myEventDispatcher.addListener(changeListener);
  }

}

package com.karateca.jstoolbox.generatemethod;

import com.intellij.openapi.application.ApplicationManager;
import com.intellij.openapi.editor.Document;
import com.intellij.openapi.project.Project;
import com.intellij.util.EventDispatcher;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.util.ArrayList;
import java.util.List;

/**
 * @author Andres Dominguez
 */
class ParentNamespaceFinder {

  private final Document document;
  private final EventDispatcher<ChangeListener> myEventDispatcher =
      EventDispatcher.create(ChangeListener.class);
  private final Project project;
  private List<Function> functionNames;
  private String currentNamespace;
  private String parentNamespace;

  List<Function> getFunctionNames() {
    return functionNames;
  }

  String getCurrentNamespace() {
    return currentNamespace;
  }

  String getParentNamespace() {
    return parentNamespace;
  }

  public ParentNamespaceFinder(Document document, Project project) {
    this.document = document;
    this.project = project;
  }

  public void findParentClass() {
    ApplicationManager.getApplication().runReadAction(new Runnable() {
      @Override
      public void run() {
        functionNames = new ArrayList<Function>();

        HierarchyFinder hierarchyFinder = new HierarchyFinder(project, document);
        HierarchyResults parents = hierarchyFinder.findParents();

        if (parents == null) {
          return;
        }

        for (Document doc : parents.getHierarchy()) {
          ClassFinder finder = new ClassFinder(doc);
          functionNames.addAll(finder.getSortedMethods());
        }

        currentNamespace = parents.getCurrentClass();
        parentNamespace = parents.getParentClass();
        functionNames = getFunctionNames();

        broadcastReady();
      }
    });
  }

  private void broadcastReady() {
    myEventDispatcher.getMulticaster().stateChanged(new ChangeEvent("ParentNamespaceFound"));
  }

  /**
   * Register for change events.
   *
   * @param changeListener The listener to be added.
   */
  public void addResultsReadyListener(ChangeListener changeListener) {
    myEventDispatcher.addListener(changeListener);
  }

}

fix Null pointer exception when you override on empty file