001    /*
002     * Copyright 2010-2014 JetBrains s.r.o.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package org.jetbrains.jet.lang.resolve.java.structure;
018    
019    import org.jetbrains.annotations.NotNull;
020    import org.jetbrains.annotations.Nullable;
021    import org.jetbrains.jet.lang.descriptors.PropertyDescriptor;
022    import org.jetbrains.jet.lang.resolve.constants.CompileTimeConstant;
023    
024    import java.util.Iterator;
025    import java.util.ServiceLoader;
026    
027    public abstract class JavaPropertyInitializerEvaluator {
028        private static JavaPropertyInitializerEvaluator instance;
029    
030        @NotNull
031        public static JavaPropertyInitializerEvaluator getInstance() {
032            if (instance == null) {
033                Iterator<JavaPropertyInitializerEvaluator> iterator =
034                        ServiceLoader.load(JavaPropertyInitializerEvaluator.class, JavaPropertyInitializerEvaluator.class.getClassLoader()).iterator();
035                assert iterator.hasNext() : "No service found: " + JavaPropertyInitializerEvaluator.class.getName();
036                instance = iterator.next();
037            }
038            return instance;
039        }
040    
041        @Nullable
042        public abstract CompileTimeConstant<?> getInitializerConstant(@NotNull JavaField field, @NotNull PropertyDescriptor descriptor);
043    }