001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.generic;
020
021/**
022 * Thrown by {@link InstructionList} when one or multiple disposed instructions are still being referenced by an {@link InstructionTargeter} object. I.e. the
023 * {@link InstructionTargeter} has to be notified that (one of) the {@link InstructionHandle} it is referencing is being removed from the
024 * {@link InstructionList} and thus not valid anymore.
025 *
026 * <p>
027 * Making this an exception instead of a return value forces the user to handle these case explicitly in a try { ... } catch. The following code illustrates how
028 * this may be done:
029 * </p>
030 *
031 * <pre>
032 *     ...
033 *     try {
034 *         il.delete(start_ih, end_ih);
035 *     } catch (TargetLostException e) {
036 *         for (InstructionHandle target : e.getTargets()) {
037 *             for (InstructionTargeter targeter : target.getTargeters()) {
038 *                 targeter.updateTarget(target, new_target);
039 *             }
040 *         }
041 *     }
042 * </pre>
043 *
044 * @see InstructionHandle
045 * @see InstructionList
046 * @see InstructionTargeter
047 */
048public final class TargetLostException extends Exception {
049
050    private static final long serialVersionUID = -6857272667645328384L;
051
052    /** The target instruction handles that were lost. */
053    private final InstructionHandle[] targets;
054
055    /**
056     * Constructs a TargetLostException.
057     *
058     * @param targets The instruction handles.
059     * @param message The exception message.
060     */
061    TargetLostException(final InstructionHandle[] targets, final String message) {
062        super(message);
063        this.targets = targets;
064    }
065
066    /**
067     * Gets the list of instructions still being targeted.
068     *
069     * @return list of instructions still being targeted.
070     */
071    public InstructionHandle[] getTargets() {
072        return targets;
073    }
074}