1 /*
2  * Copyright (C) 2018 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 
17 import java.lang.ref.Reference;
18 import java.lang.ref.WeakReference;
19 
20 public class Main {
main(String[] args)21     public static void main(String[] args) {
22         System.out.println("Starting");
23         WeakReference wrefs[] = new WeakReference[5];
24         String str0 = generateString("String", 0);
25         String str1 = generateString("String", 1);
26         String str2 = generateString("String", 2);
27         String str3 = generateString("String", 3);
28         String str4 = generateString("String", 4);
29         wrefs[0] = new WeakReference(str0);
30         wrefs[1] = new WeakReference(str1);
31         wrefs[2] = new WeakReference(str2);
32         wrefs[3] = new WeakReference(str3);
33         wrefs[4] = new WeakReference(str4);
34         // Clear a couple as a soundness check.
35         str1 = null;
36         str2 = null;
37         // str<n> dead here; in the future we will possibly reuse the registers.
38         // Give the compiler something to fill the registers with.
39         String str5 = generateString("String", 5);
40         String str6 = generateString("String", 6);
41         String str7 = generateString("String", 7);
42         String str8 = generateString("String", 8);
43         String str9 = generateString("String", 9);
44         Runtime.getRuntime().gc();
45         for (int i = 0; i < 5; ++i) {
46           if (wrefs[i].get() != null) {
47             System.out.println("Reference " + i + " was live.");
48           }
49         }
50         Reference.reachabilityFence(str0);
51         Reference.reachabilityFence(str1);
52         Reference.reachabilityFence(str2);
53         Reference.reachabilityFence(str3);
54         Reference.reachabilityFence(str4);
55         System.out.println("Finished");
56     }
57 
generateString(String base, int num)58     private static String generateString(String base, int num) {
59         return base + num;
60     }
61 }
62