Tue, 14 May 2013 11:11:09 -0700
8012556: Implement lambda methods on interfaces as static
8006140: Javac NPE compiling Lambda expression on initialization expression of static field in interface
Summary: Lambdas occurring in static contexts or those not needing instance information should be generated into static methods. This has long been the case for classes. However, as a work-around to the lack of support for statics on interfaces, interface lambda methods have been generated into default methods. For lambdas in interface static contexts (fields and static methods) this causes an NPE in javac because there is no 'this'. MethodHandles now support static methods on interfaces. This changeset allows lambda methods to be generated as static interface methods. An existing bug in Hotspot (8013875) is exposed in a test when the "-esa" flag is used. This test and another test that already exposed this bug have been marked with @ignore.
Reviewed-by: mcimadamore
1 /*
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24 */
26 /**
27 * Determines if the input object matches some criteria.
28 *
29 * <p>All predicate implementations are expected to:
30 * <ul>
31 * <li>Provide stable results such that for any {@code t} the result of two
32 * {@code eval} operations are always equivalent. ie.<pre>
33 * boolean one = predicate.test(a);
34 * boolean two = predicate.test(a);
35 *
36 * assert one == two;
37 * </pre></li>
38 * <li>Equivalent input objects should map to equivalent output objects. ie.<pre>
39 * assert a.equals(b); // a and b are equivalent
40 *
41 * boolean x = predicate.test(a);
42 * boolean y = predicate.test(ab;
43 *
44 * assert x == y; // their test results should be the same.
45 * </pre></li>
46 * <li>The predicate should not modify the input object in any way that would
47 * change the evaluation.</li>
48 * <li>When used for aggregate operations upon many elements predicates
49 * should not assume that the {@code test} operation will be called upon
50 * elements in any specific order.</li>
51 * </ul>
52 *
53 * @param <T> the type of input objects provided to {@code test}.
54 */
55 public interface TPredicate<T> {
57 /**
58 * Return {@code true} if the input object matches some criteria.
59 *
60 * @param t the input object.
61 * @return {@code true} if the input object matched some criteria.
62 */
63 boolean test(T t);
64 }