1 /* 2 * Copyright (C) 2012 Google Inc. 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.google.caliper.memory; 18 19 /** 20 * A visitor that controls an object traversal. Implementations 21 * of this interface are passed to {@link ObjectExplorer} exploration methods. 22 * 23 * @param <T> the type of the result that this visitor returns 24 * (can be defined as {@code Void} to denote no result}. 25 * 26 * @see ObjectExplorer 27 */ 28 public interface ObjectVisitor<T> { 29 /** 30 * Visits an explored value (the whole chain from the root object 31 * leading to the value is provided), and decides whether to continue 32 * the exploration of that value. 33 * 34 * <p>In case the explored value is either primitive or {@code null} 35 * (e.g., if {@code chain.isPrimitive() || chain.getValue() == null}), 36 * the return value is meaningless and is ignored. 37 * 38 * @param chain the chain that leads to the explored value. 39 * @return {@link Traversal#EXPLORE} to denote that the visited object 40 * should be further explored, or {@link Traversal#SKIP} to avoid 41 * exploring it. 42 */ visit(Chain chain)43 Traversal visit(Chain chain); 44 45 /** 46 * Returns an arbitrary value (presumably constructed during the object 47 * graph traversal). 48 */ result()49 T result(); 50 51 /** 52 * Constants that denote how the traversal of a given object (chain) 53 * should continue. 54 */ 55 enum Traversal { 56 /** 57 * The visited object should be further explored. 58 */ 59 EXPLORE, 60 61 /** 62 * The visited object should not be explored. 63 */ 64 SKIP 65 } 66 } 67