EmptyIterator.java revision 9330:8b1f1c2a400f 
1/*
2 * Copyright (c) 2007, 2012, 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 8004928
27 * @summary Test empty iterators, enumerations, and collections
28 */
29
30import static java.util.Collections.*;
31import java.util.*;
32
33public class EmptyIterator {
34
35    void test(String[] args) throws Throwable {
36        testEmptyCollection(Collections.<Object>emptyList());
37        testEmptyCollection(Collections.<Object>emptySet());
38
39        testEmptyMap(Collections.<Object, Object>emptyMap());
40
41        Hashtable<Object, Object> emptyTable = new Hashtable<Object, Object>();
42        testEmptyEnumeration(emptyTable.keys());
43        testEmptyEnumeration(emptyTable.elements());
44        testEmptyIterator(emptyTable.keySet().iterator());
45        testEmptyIterator(emptyTable.values().iterator());
46        testEmptyIterator(emptyTable.entrySet().iterator());
47
48        final Enumeration<EmptyIterator> finalEmptyTyped =
49            Collections.emptyEnumeration();
50        testEmptyEnumeration(finalEmptyTyped);
51
52        final Enumeration finalEmptyAbstract =
53            Collections.emptyEnumeration();
54        testEmptyEnumeration(finalEmptyAbstract);
55
56        @SuppressWarnings("unchecked") Iterator<?> x =
57            new sun.tools.java.MethodSet()
58            .lookupName(sun.tools.java.Identifier.lookup(""));
59        testEmptyIterator(x);
60    }
61
62    <T> void testEmptyEnumeration(final Enumeration<T> e) {
63        check(e == emptyEnumeration());
64        check(! e.hasMoreElements());
65        THROWS(NoSuchElementException.class,
66               new F(){void f(){ e.nextElement(); }});
67    }
68
69    <T> void testEmptyIterator(final Iterator<T> it) {
70        check(it == emptyIterator());
71        check(! it.hasNext());
72        THROWS(NoSuchElementException.class,
73               new F(){void f(){ it.next(); }});
74        THROWS(IllegalStateException.class,
75               new F(){void f(){ it.remove(); }});
76    }
77
78    void testEmptyMap(Map<Object, Object> m) {
79        check(m == emptyMap());
80        check(m.entrySet().iterator() ==
81              Collections.<Map.Entry<Object,Object>>emptyIterator());
82        check(m.values().iterator() == emptyIterator());
83        check(m.keySet().iterator() == emptyIterator());
84        equal(m, unmodifiableMap(m));
85
86        testEmptyCollection(m.keySet());
87        testEmptyCollection(m.entrySet());
88        testEmptyCollection(m.values());
89    }
90
91    <E> void testToArray(final Collection<E> c) {
92        Object[] a = c.toArray();
93        equal(a.length, 0);
94        equal(a.getClass().getComponentType(), Object.class);
95        THROWS(NullPointerException.class,
96               new F(){void f(){ c.toArray((Object[])null); }});
97
98        {
99            String[] t = new String[0];
100            check(c.toArray(t) == t);
101        }
102
103        {
104            String[] t = nCopies(10, "").toArray(new String[0]);
105            check(c.toArray(t) == t);
106            check(t[0] == null);
107            for (int i=1; i<t.length; i++)
108                check(t[i] == "");
109        }
110    }
111
112    <E> void testEmptyCollection(final Collection<E> c) {
113        testEmptyIterator(c.iterator());
114
115        check(c.iterator() == emptyIterator());
116        if (c instanceof List)
117            check(((List<?>)c).listIterator() == emptyListIterator());
118
119        testToArray(c);
120    }
121
122    //--------------------- Infrastructure ---------------------------
123    volatile int passed = 0, failed = 0;
124    void pass() {passed++;}
125    void fail() {failed++; Thread.dumpStack();}
126    void fail(String msg) {System.err.println(msg); fail();}
127    void unexpected(Throwable t) {failed++; t.printStackTrace();}
128    void check(boolean cond) {if (cond) pass(); else fail();}
129    void equal(Object x, Object y) {
130        if (x == null ? y == null : x.equals(y)) pass();
131        else fail(x + " not equal to " + y);}
132    public static void main(String[] args) throws Throwable {
133        new EmptyIterator().instanceMain(args);}
134    void instanceMain(String[] args) throws Throwable {
135        try {test(args);} catch (Throwable t) {unexpected(t);}
136        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
137        if (failed > 0) throw new AssertionError("Some tests failed");}
138    abstract class F {abstract void f() throws Throwable;}
139    void THROWS(Class<? extends Throwable> k, F... fs) {
140        for (F f : fs)
141            try {f.f(); fail("Expected " + k.getName() + " not thrown");}
142            catch (Throwable t) {
143                if (k.isAssignableFrom(t.getClass())) pass();
144                else unexpected(t);}}
145}
146