1 /*
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23 
24 /*
25  * @test
26  * @bug 8209824
27  * @summary per latest JDK code coverage report, 2 methods replaceStaleEntry
28  *          and prevIndex in ThreadLocal.ThreadLocalMap are not touched
29  *          by any JDK regression tests, this is to trigger the code paths.
30  * @modules java.base/java.lang:+open
31  * @run testng ReplaceStaleEntry
32  */
33 
34 import java.lang.reflect.Field;
35 import java.util.HashMap;
36 import java.util.Map;
37 
38 import static org.testng.Assert.assertEquals;
39 import org.testng.annotations.BeforeClass;
40 import org.testng.annotations.Test;
41 
42 public class ReplaceStaleEntry {
43 
44     public static int INITIAL_CAPACITY;
45 
46     @BeforeClass
setup()47     public static void setup() throws Exception {
48         Class<?> clazz = Class.forName("java.lang.ThreadLocal$ThreadLocalMap");
49         Field f = clazz.getDeclaredField("INITIAL_CAPACITY");
50         f.setAccessible(true);
51         INITIAL_CAPACITY = f.getInt(null);
52         System.out.println("INITIAL_CAPACITY: " + INITIAL_CAPACITY);
53     }
54 
55     /**
56      * This test triggers the code path to replaceStaleEntry, so as prevIndex is
57      * triggered too as it's called by replaceStaleEntry.
58      * The code paths must be triggered by reusing an already used entry in the
59      * map's entry table. The code below
60      *  1. first occupies the entries
61      *  2. then expunges the entries by removing strong references to thread locals
62      *  3. then reuse some of entries by adding more thread locals to the thread
63      * and, the above steps are run for several times by adding more and more
64      * thread locals, also trigger rehash of the map.
65      */
66     @Test
test()67     public static void test() {
68         Map<Integer, ThreadLocal> locals = new HashMap<>();
69         for (int j = 1; j < 32; j *= 2) {
70             int loop = INITIAL_CAPACITY * j;
71             for (int i = 0; i < loop; i++) {
72                 ThreadLocal l = new ThreadLocal<Integer>();
73                 l.set(i);
74                 locals.put(i, l);
75             }
76             locals.keySet().stream().forEach(i -> {
77                 assertEquals((int)locals.get(i).get(), (int)i, "Unexpected thread local value!");
78             });
79             locals.clear();
80             System.gc();
81         }
82     }
83 }
84