checker/tests/nullness/SetIteratorTest.java

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

public class SetIteratorTest {

  private SortedSet<String> nodes;
  private Map<String, TreeMap<String, TreeSet<String>>> edges;

  public SetIteratorTest() {
    nodes = new TreeSet<String>();
    edges = new HashMap<String, TreeMap<String, TreeSet<String>>>();
  }

  public Set<String> listNodes() {
    return Collections.unmodifiableSet(nodes);
  }

  public String listChildren(String parentNode) {
    String childrenString = "";

    if (edges.get(parentNode) != null) {
      for (String childNode : edges.get(parentNode).keySet()) {
        // :: error: (dereference.of.nullable)
        edges.get(parentNode).toString();
        for (String childNodeEdgeX : edges.get(parentNode).get(childNode)) {
          childrenString += " " + childNode + "(" + childNodeEdgeX + ")";
        }
      }
    }

    return childrenString;
  }

  public void listChildren2(String parentNode) {
    if (edges.get(parentNode) != null) {
      Iterator<String> itor = edges.get(parentNode).keySet().iterator();
      edges.get(parentNode).toString();
      String s = itor.next();
      // :: error: (dereference.of.nullable)
      edges.get(parentNode).toString();
    }
  }

  public boolean containsNode(String node) {
    return nodes.contains(node);
  }
}