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      1 /*
      2  * Copyright 2016 Federico Tomassetti
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.github.javaparser.symbolsolver.logic;
     18 
     19 import com.github.javaparser.resolution.MethodUsage;
     20 import com.github.javaparser.resolution.declarations.ResolvedReferenceTypeDeclaration;
     21 import com.github.javaparser.resolution.types.ResolvedType;
     22 
     23 import java.lang.reflect.Method;
     24 import java.lang.reflect.Parameter;
     25 import java.util.Arrays;
     26 import java.util.List;
     27 import java.util.Optional;
     28 import java.util.Set;
     29 import java.util.stream.Collectors;
     30 
     31 /**
     32  * @author Federico Tomassetti
     33  */
     34 public final class FunctionalInterfaceLogic {
     35 
     36     private FunctionalInterfaceLogic() {
     37         // prevent instantiation
     38     }
     39 
     40     /**
     41      * Get the functional method defined by the type, if any.
     42      */
     43     public static Optional<MethodUsage> getFunctionalMethod(ResolvedType type) {
     44         if (type.isReferenceType() && type.asReferenceType().getTypeDeclaration().isInterface()) {
     45             return getFunctionalMethod(type.asReferenceType().getTypeDeclaration());
     46         } else {
     47             return Optional.empty();
     48         }
     49     }
     50 
     51     /**
     52      * Get the functional method defined by the type, if any.
     53      */
     54     public static Optional<MethodUsage> getFunctionalMethod(ResolvedReferenceTypeDeclaration typeDeclaration) {
     55         //We need to find all abstract methods
     56         Set<MethodUsage> methods = typeDeclaration.getAllMethods().stream()
     57                 .filter(m -> m.getDeclaration().isAbstract())
     58                 // Remove methods inherited by Object:
     59                 // Consider the case of Comparator which define equals. It would be considered a functional method.
     60                 .filter(m -> !declaredOnObject(m))
     61                 .collect(Collectors.toSet());
     62 
     63         if (methods.size() == 1) {
     64             return Optional.of(methods.iterator().next());
     65         } else {
     66             return Optional.empty();
     67         }
     68     }
     69 
     70     public static boolean isFunctionalInterfaceType(ResolvedType type) {
     71         return getFunctionalMethod(type).isPresent();
     72     }
     73 
     74     private static String getSignature(Method m) {
     75         return String.format("%s(%s)", m.getName(), String.join(", ", Arrays.stream(m.getParameters()).map(p -> toSignature(p)).collect(Collectors.toList())));
     76     }
     77 
     78     private static String toSignature(Parameter p) {
     79         return p.getType().getCanonicalName();
     80     }
     81 
     82     private static List<String> OBJECT_METHODS_SIGNATURES = Arrays.stream(Object.class.getDeclaredMethods())
     83             .map(method -> getSignature(method))
     84             .collect(Collectors.toList());
     85 
     86     private static boolean declaredOnObject(MethodUsage m) {
     87         return OBJECT_METHODS_SIGNATURES.contains(m.getDeclaration().getSignature());
     88     }
     89 }
     90