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23 
24 package vm.mlvm.share;
25 
26 import java.util.LinkedList;
27 import java.util.List;
28 
29 /**
30  * The base class for Mlvm tests checking various OOM Errors.
31  * Subclasses are expected to implement {@link #eatMemory(List)}/
32  * {@link checkOOME(OutOfMemoryError)} methods consuming memory in various ways.
33  */
34 public abstract class MlvmOOMTest extends MlvmTest {
35     private static Object garbage;
36 
37     /**
38      * A template method.
39      * Implements logic of the tests:
40      * consumes memory in loop until OOM is thrown, checks the OOM type.
41      */
42     @Override
run()43     public final boolean run() {
44         Env.display("Test started.");
45         LinkedList<Object> objects = new LinkedList<Object>();
46         // to trick EA
47         garbage = objects;
48         try {
49             eatMemory(objects);
50         } catch (OutOfMemoryError oome) {
51             objects.clear();
52             Env.display("Caught OOME : " + oome.getMessage());
53             checkOOME(oome);
54             return true;
55         }
56         throw new RuntimeException("TEST FAIL : no OOME");
57     }
58 
59     /**
60      * Consumes memory.
61      * Subclasses implement their logic of memory consuming. Created objects are expected
62      * to be stored in the given parameter.
63      * The normal termination of the method is throwing OOM exception, which will be checked
64      * by the {@link #checkOOME(OutOfMemoryError)}
65      * Not throwing the OOM will be interpreted as test failure.
66      * @param garbage a list to store generated garbage
67      */
eatMemory(List<Object> garbage)68     protected abstract void eatMemory(List<Object> garbage);
69 
70     /**
71      * Checks the OOME type is expected.
72      * Method just exits if OOME is expected and throws an exeption if not.
73      * @param oome thrown by {@link #eatMemory(List)}
74      */
checkOOME(OutOfMemoryError oome)75     protected abstract void checkOOME(OutOfMemoryError oome);
76 }
77