InternersTest.java revision 1d580d0f6ee4f21eb309ba7b509d2c6d671c4044 
1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import com.google.common.base.Function;
20import com.google.common.testing.NullPointerTester;
21
22import junit.framework.TestCase;
23
24import java.lang.ref.WeakReference;
25
26/**
27 * Unit test for {@link Interners}.
28 *
29 * @author Kevin Bourrillion
30 */
31public class InternersTest extends TestCase {
32
33  public void testStrong_simplistic() {
34    String canonical = "a";
35    String not = new String("a");
36
37    Interner<String> pool = Interners.newStrongInterner();
38    assertSame(canonical, pool.intern(canonical));
39    assertSame(canonical, pool.intern(not));
40  }
41
42  public void testStrong_null() {
43    Interner<String> pool = Interners.newStrongInterner();
44    try {
45      pool.intern(null);
46      fail();
47    } catch (NullPointerException ok) {}
48  }
49
50  public void testWeak_simplistic() {
51    String canonical = "a";
52    String not = new String("a");
53
54    Interner<String> pool = Interners.newWeakInterner();
55    assertSame(canonical, pool.intern(canonical));
56    assertSame(canonical, pool.intern(not));
57  }
58
59  public void testWeak_null() {
60    Interner<String> pool = Interners.newWeakInterner();
61    try {
62      pool.intern(null);
63      fail();
64    } catch (NullPointerException ok) {}
65  }
66
67  public void testWeak_afterGC() throws InterruptedException {
68    Integer canonical = new Integer(5);
69    Integer not = new Integer(5);
70
71    Interner<Integer> pool = Interners.newWeakInterner();
72    assertSame(canonical, pool.intern(canonical));
73
74    WeakReference<Integer> signal = new WeakReference<Integer>(canonical);
75    canonical = null;
76
77    for (int i = 0; i < 3000; i++) {
78      System.gc();
79      if (signal.get() == null) { // it was collected
80        assertSame(not, pool.intern(not));
81        return;
82      }
83      Thread.sleep(1);
84    }
85    fail("reference didn't get cleaned up");
86  }
87
88  public void testAsFunction_simplistic() {
89    String canonical = "a";
90    String not = new String("a");
91
92    Function<String, String> internerFunction =
93        Interners.asFunction(Interners.<String>newStrongInterner());
94
95    assertSame(canonical, internerFunction.apply(canonical));
96    assertSame(canonical, internerFunction.apply(not));
97  }
98
99  public void testNullPointerExceptions() throws Exception {
100    new NullPointerTester().testAllPublicStaticMethods(Interners.class);
101  }
102}
103