1 /*
   2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @bug 8020968
  27  * @summary Sanity test for Function wildcard signature
  28  * @run main WalkFunction
  29  */
  30 
  31 import java.lang.StackWalker.StackFrame;
  32 import java.util.Optional;
  33 import java.util.function.Function;
  34 import java.util.stream.Stream;
  35 
  36 public class WalkFunction {
  37     private static final StackWalker walker = StackWalker.create();
  38 
  39     public static void main(String... args) throws Exception {
  40         testFunctions();
  41         testWildcards();
  42         walker.walk(counter());
  43         walker.walk(wildCounter());
  44     }
  45 
  46     private static void testFunctions() {
  47         walker.walk(Stream::count);
  48 
  49         try {
  50             walker.walk(null);
  51             throw new RuntimeException("NPE expected");
  52         } catch (NullPointerException e) {}
  53 
  54         Optional<StackFrame> result = walker.walk(WalkFunction::reduce);
  55         if (!result.get().getClassName().equals(WalkFunction.class.getName())) {
  56             throw new RuntimeException(result.get() + " expected: " + WalkFunction.class.getName());
  57         }
  58     }
  59 
  60     static Optional<StackFrame> reduce(Stream<StackFrame> stream) {
  61         return stream.reduce((r,f) -> r.getClassName().compareTo(f.getClassName()) > 0 ? f : r);
  62     }
  63 
  64     private static void testWildcards() {
  65         Function<? super Stream<? extends  StackFrame>, Void> f1 = WalkFunction::function;
  66         Function<? super Stream<? super StackFrame>, Void> f2 = WalkFunction::function;
  67         Function<? super Stream<StackFrame>, Void> f3 = WalkFunction::function;
  68         Function<Stream<? extends StackFrame>, Void> f4 = WalkFunction::function;
  69         Function<Stream<? super StackFrame>, Void> f5 = WalkFunction::function;
  70         Function<Stream<StackFrame>, Void> f6 = WalkFunction::function;
  71         walker.walk(f1);
  72         walker.walk(f2);
  73         walker.walk(f3);
  74         walker.walk(f4);
  75         walker.walk(f5);
  76         walker.walk(f6);
  77     }
  78 
  79     private static Void function(Stream<?> s) {
  80         return null;
  81     }
  82 
  83     private static Function<Stream<?>, Long> wildCounter() {
  84         return Stream::count;
  85     }
  86     private static <T> Function<Stream<T>, Long> counter() {
  87         return Stream::count;
  88     }
  89 }