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      1 // Copyright 2017 The Bazel Authors. All rights reserved.
      2 //
      3 // Licensed under the Apache License, Version 2.0 (the "License");
      4 // you may not use this file except in compliance with the License.
      5 // You may obtain a copy of the License at
      6 //
      7 //    http://www.apache.org/licenses/LICENSE-2.0
      8 //
      9 // Unless required by applicable law or agreed to in writing, software
     10 // distributed under the License is distributed on an "AS IS" BASIS,
     11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 // See the License for the specific language governing permissions and
     13 // limitations under the License.
     14 package com.google.devtools.build.android.desugar.testdata.java8;
     15 
     16 import java.util.List;
     17 import java.util.function.Function;
     18 import java.util.stream.Collectors;
     19 
     20 /** Desugaring test input interface that includes a default method and a static method. */
     21 public interface FunctionWithDefaultMethod<T extends Number> extends Function<T, T> {
     22 
     23   @Override
     24   T apply(T input);
     25 
     26   static <T extends Number> Function<T, Long> toLong() {
     27     return input -> input.longValue();
     28   }
     29 
     30   default T twice(T input) {
     31     return apply(apply(input));
     32   }
     33 
     34   /** Don't call this method from tests, it won't work since Desugar moves it! */
     35   static FunctionWithDefaultMethod<Integer> inc(int add) {
     36     return input -> input + add;
     37   }
     38 
     39   /**
     40    * Implementation of {@link FunctionWithDefaultMethod} that overrides the default method.
     41    * Also declares static methods the test uses to exercise the code in this file.
     42    */
     43   public static class DoubleInts implements FunctionWithDefaultMethod<Integer> {
     44     @Override
     45     public Integer apply(Integer input) {
     46       return 2 * input;
     47     }
     48 
     49     @Override
     50     public Integer twice(Integer input) {
     51       return 5 * input; // deliberately wrong :)
     52     }
     53 
     54     public static List<Long> add(List<Integer> ints, int add) {
     55       return ints.stream().map(inc(add)).map(toLong()).collect(Collectors.toList());
     56     }
     57 
     58     public static FunctionWithDefaultMethod<Integer> doubleLambda() {
     59       return input -> 2 * input;
     60     }
     61 
     62     public static FunctionWithDefaultMethod<Integer> incTwice(int add) {
     63       return inc(add)::twice;
     64     }
     65 
     66     public static FunctionWithDefaultMethod<Integer> times5() {
     67       return new DoubleInts2()::twice;
     68     }
     69 
     70     public static Function<Integer, FunctionWithDefaultMethod<Integer>> incFactory() {
     71       return FunctionWithDefaultMethod::inc;
     72     }
     73   }
     74 
     75   /** Empty subclass that explicitly implements the interface the superclass already implements. */
     76   public static class DoubleInts2 extends DoubleInts implements FunctionWithDefaultMethod<Integer> {
     77   }
     78 }
     79