1 /*
   2  * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @bug 5017904 6356890
  27  * @summary Test empty iterators, enumerations, and collections
  28  */
  29 
  30 import java.util.*;
  31 import static java.util.Collections.*;
  32 
  33 public class EmptyIterator {
  34 
  35     void test(String[] args) throws Throwable {
  36         testEmptyCollection(Collections.<Object>emptyList());
  37         testEmptyCollection(Collections.<Object>emptySet());
  38         testEmptyCollection(new java.util.concurrent.
  39                             SynchronousQueue<Object>());
  40 
  41         testEmptyMap(Collections.<Object, Object>emptyMap());
  42 
  43         Hashtable<Object, Object> emptyTable = new Hashtable<Object, Object>();
  44         testEmptyEnumeration(emptyTable.keys());
  45         testEmptyEnumeration(emptyTable.elements());
  46         testEmptyIterator(emptyTable.keySet().iterator());
  47         testEmptyIterator(emptyTable.values().iterator());
  48         testEmptyIterator(emptyTable.entrySet().iterator());
  49 
  50         testEmptyEnumeration(javax.swing.tree.DefaultMutableTreeNode
  51                              .EMPTY_ENUMERATION);
  52         testEmptyEnumeration(javax.swing.text.SimpleAttributeSet
  53                              .EMPTY.getAttributeNames());
  54 
  55         @SuppressWarnings("unchecked") Iterator<?> x =
  56             new sun.tools.java.MethodSet()
  57             .lookupName(sun.tools.java.Identifier.lookup(""));
  58         testEmptyIterator(x);
  59     }
  60 
  61     <T> void testEmptyEnumeration(final Enumeration<T> e) {
  62         check(e == emptyEnumeration());
  63         check(! e.hasMoreElements());
  64         THROWS(NoSuchElementException.class,
  65                new F(){void f(){ e.nextElement(); }});
  66     }
  67 
  68     <T> void testEmptyIterator(final Iterator<T> it) {
  69         check(it == emptyIterator());
  70         check(! it.hasNext());
  71         THROWS(NoSuchElementException.class,
  72                new F(){void f(){ it.next(); }});
  73         THROWS(IllegalStateException.class,
  74                new F(){void f(){ it.remove(); }});
  75     }
  76 
  77     void testEmptyMap(Map<Object, Object> m) {
  78         check(m == emptyMap());
  79         check(m.entrySet().iterator() ==
  80               Collections.<Map.Entry<Object,Object>>emptyIterator());
  81         check(m.values().iterator() == emptyIterator());
  82         check(m.keySet().iterator() == emptyIterator());
  83         equal(m, unmodifiableMap(m));
  84 
  85         testEmptyCollection(m.keySet());
  86         testEmptyCollection(m.entrySet());
  87         testEmptyCollection(m.values());
  88     }
  89 
  90     <E> void testToArray(final Collection<E> c) {
  91         Object[] a = c.toArray();
  92         equal(a.length, 0);
  93         equal(a.getClass().getComponentType(), Object.class);
  94         THROWS(NullPointerException.class,
  95                new F(){void f(){ c.toArray((Object[])null); }});
  96 
  97         {
  98             String[] t = new String[0];
  99             check(c.toArray(t) == t);
 100         }
 101 
 102         {
 103             String[] t = nCopies(10, "").toArray(new String[0]);
 104             check(c.toArray(t) == t);
 105             check(t[0] == null);
 106             for (int i=1; i<t.length; i++)
 107                 check(t[i] == "");
 108         }
 109     }
 110 
 111     <E> void testEmptyCollection(final Collection<E> c) {
 112         testEmptyIterator(c.iterator());
 113 
 114         check(c.iterator() == emptyIterator());
 115         if (c instanceof List)
 116             check(((List<?>)c).listIterator() == emptyListIterator());
 117 
 118         testToArray(c);
 119     }
 120 
 121     //--------------------- Infrastructure ---------------------------
 122     volatile int passed = 0, failed = 0;
 123     void pass() {passed++;}
 124     void fail() {failed++; Thread.dumpStack();}
 125     void fail(String msg) {System.err.println(msg); fail();}
 126     void unexpected(Throwable t) {failed++; t.printStackTrace();}
 127     void check(boolean cond) {if (cond) pass(); else fail();}
 128     void equal(Object x, Object y) {
 129         if (x == null ? y == null : x.equals(y)) pass();
 130         else fail(x + " not equal to " + y);}
 131     public static void main(String[] args) throws Throwable {
 132         new EmptyIterator().instanceMain(args);}
 133     void instanceMain(String[] args) throws Throwable {
 134         try {test(args);} catch (Throwable t) {unexpected(t);}
 135         System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
 136         if (failed > 0) throw new AssertionError("Some tests failed");}
 137     abstract class F {abstract void f() throws Throwable;}
 138     void THROWS(Class<? extends Throwable> k, F... fs) {
 139         for (F f : fs)
 140             try {f.f(); fail("Expected " + k.getName() + " not thrown");}
 141             catch (Throwable t) {
 142                 if (k.isAssignableFrom(t.getClass())) pass();
 143                 else unexpected(t);}}
 144 }