code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.jtreg.util.Collections;
  
  /*
   * Copyright 2007 Sun Microsystems, Inc.  All Rights Reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   */
  
  /*
   * @test
   * @bug 6409434
   * @summary Test behavior of nulls in checked collections
   */
  
  import java.util.*;
  import static java.util.Collections.*;
  
  @SuppressWarnings({"unchecked","serial"})
  public class CheckedNull {
  
      void test(String[] args) throws Throwable {
          testCollection(Collections.checkedCollection(
                             new ArrayList<String>(), String.class));
          testCollection(Collections.checkedList(
                             new ArrayList<String>(), String.class));
          testCollection(Collections.checkedSet(
                             new HashSet<String>(), String.class));
  
          final Comparator nullLow = new Comparator() {
                  public int compare(Object x, Object y) {
                      return x == y ?  0 :
                          x == null ? -1 :
                          y == null ?  1 :
                          ((Comparable)x).compareTo(y); }};
          testCollection(Collections.checkedSortedSet(
                             new TreeSet<String>(nullLow), String.class));
  
          testMap(Collections.checkedMap(
                      new HashMap<String, String>(),
                      String.class, String.class));;
      }
  
      ClassCastException cce(F f) {
          try { f.f(); fail(); return null; }
          catch (ClassCastException cce) { pass(); return cce; }
          catch (Throwable t) { unexpected(t); return null; }
      }
  
      void equalCCE(F ... fs) {
          String detailMessage = null;
          for (F f : fs)
              if (detailMessage == null)
                  detailMessage = cce(f).getMessage();
              else
                  equal(detailMessage, cce(f).getMessage());
      }
  
      void add(Collection c, Object o) {
          int s = c.size();
          check(! c.contains(o));
          check(c.add(o));
          check(c.contains(o));
          equal(c.size(), s+1);
          check(c.remove(o));
          check(! c.contains(o));
          check(c.addAll(singleton(o)));
          check(c.contains(o));
          equal(c.size(), s+1);
          check(c.remove(o));
          equal(c.size(), s);
      }
  
      void testCollection(final Collection c) {
          try {
              check(c.isEmpty());
              add(c, null);
              add(c, "foo");
  
              check(c.add("bar"));
              add(c, null);
              add(c, "foo");
  
              equalCCE(
                  new F(){void f(){ c.add(1); }},
                  new F(){void f(){ c.addAll(singleton(1)); }});
  
          } catch (Throwable t) { unexpected(t); }
      }
  
      void put(Map m, Object k, Object v) {
          int s = m.size();
          check(! m.containsKey(k));
          check(! m.containsValue(v));
          equal(null, m.put(k, v));
          check(m.containsKey(k));
          check(m.containsValue(v));
          equal(m.size(), s+1);
          equal(v, m.remove(k));
          check(! m.containsKey(k));
          check(! m.containsValue(v));
          m.putAll(singletonMap(k,v));
          check(m.containsKey(k));
          check(m.containsValue(v));
          equal(m.size(), s+1);
          equal(v,m.remove(k));
          equal(m.size(), s);
      }
  
      void testMap(final Map m) {
          try {
              check(m.isEmpty());
  
              put(m, "foo", null);
              put(m, null, "foo");
              put(m, null, null);
              put(m, "foo", "bar");
  
              m.put("a", "b");
  
              put(m, "foo", null);
              put(m, null, "foo");
              put(m, null, null);
              put(m, "foo", "bar");
  
              equalCCE(
                  new F(){void f(){ m.put(1, "foo"); }},
                  new F(){void f(){ m.putAll(singletonMap(1, "foo")); }});
  
              final Collection cheater = new ArrayList() {
                      public boolean contains(Object o) {
                          if (o instanceof Map.Entry)
                              ((Map.Entry)o).setValue(1);
                          return false; }};
  
              equalCCE(
                  new F(){void f(){ m.put("foo", 1); }},
                  new F(){void f(){ m.putAll(singletonMap("foo", 1)); }},
                  new F(){void f(){
                      ((Map.Entry)m.entrySet().iterator().next()).setValue(1); }},
                  new F(){void f(){
                      m.entrySet().removeAll(cheater);}},
                  new F(){void f(){
                      m.entrySet().retainAll(cheater);}});
  
              equalCCE(
                  new F(){void f(){ m.put(3, 1); }},
                  new F(){void f(){ m.putAll(singletonMap(3, 1)); }});
  
              equal(m.size(), 1);
              equal(m.keySet(), singleton("a"));
              equal(m.entrySet(),
                    singleton(new AbstractMap.SimpleImmutableEntry("a","b")));
  
          } catch (Throwable t) { unexpected(t); }
      }
  
      //--------------------- Infrastructure ---------------------------
      volatile int passed = 0, failed = 0;
      void pass() {passed++;}
      void fail() {failed++; Thread.dumpStack();}
      void fail(String msg) {System.err.println(msg); fail();}
      void unexpected(Throwable t) {failed++; t.printStackTrace();}
      void check(boolean cond) {if (cond) pass(); else fail();}
      void equal(Object x, Object y) {
          if (x == null ? y == null : x.equals(y)) pass();
          else fail(x + " not equal to " + y);}
      public static void main(String[] args) throws Throwable {
          new CheckedNull().instanceMain(args);}
      void instanceMain(String[] args) throws Throwable {
          try {test(args);} catch (Throwable t) {unexpected(t);}
          System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
          if (failed > 0) throw new AssertionError("Some tests failed");}
      abstract class F {abstract void f() throws Throwable;}
  }
  