1/*
2 * Copyright (C) 2008 The Android Open Source Project
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
17import java.lang.ref.*;
18
19public class InternedString {
20    public static final String CONST = "Class InternedString";
21
22    public static void run() {
23        System.out.println("InternedString.run");
24        testImmortalInternedString();
25        testDeadInternedString();
26    }
27
28    private static WeakReference<String> makeWeakString() {
29        String s = "blah";
30        s = s + s;
31        WeakReference<String> strRef = new WeakReference<String>(s.intern());
32        return strRef;
33    }
34
35    private static void testDeadInternedString() {
36        WeakReference<String> strRef = makeWeakString();
37        Runtime.getRuntime().gc();
38        // "blahblah" should disappear from the intern list
39        Main.assertTrue(strRef.get() == null);
40    }
41
42    private static void testImmortalInternedString() {
43        WeakReference strRef = new WeakReference<String>(CONST.intern());
44        Runtime.getRuntime().gc();
45        // Class constant string should be entered to the interned table when
46        // loaded
47        Main.assertTrue(CONST == CONST.intern());
48        // and it should survive the gc
49        Main.assertTrue(strRef.get() != null);
50
51        String s = CONST;
52        // "Class InternedString" should remain on the intern list
53        strRef = new WeakReference<String>(s.intern());
54        // Kill s, otherwise the string object is still accessible from root set
55        s = "";
56        Runtime.getRuntime().gc();
57        Main.assertTrue(strRef.get() == CONST);
58    }
59}
60