001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.generic;
019
020import org.apache.bcel.ExceptionConst;
021
022/**
023 * CHECKCAST - Check whether object is of given type
024 * <PRE>Stack: ..., objectref -&gt; ..., objectref</PRE>
025 *
026 */
027public class CHECKCAST extends CPInstruction implements LoadClass, ExceptionThrower, StackProducer,
028        StackConsumer {
029
030    /**
031     * Empty constructor needed for Instruction.readInstruction.
032     * Not to be used otherwise.
033     */
034    CHECKCAST() {
035    }
036
037
038    /** Check whether object is of given type
039     * @param index index to class in constant pool
040     */
041    public CHECKCAST(final int index) {
042        super(org.apache.bcel.Const.CHECKCAST, index);
043    }
044
045
046    /** @return exceptions this instruction may cause
047     */
048    @Override
049    public Class<?>[] getExceptions() {
050        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_CLASS_AND_INTERFACE_RESOLUTION,
051            ExceptionConst.CLASS_CAST_EXCEPTION);
052    }
053
054
055    @Override
056    public ObjectType getLoadClassType( final ConstantPoolGen cpg ) {
057        Type t = getType(cpg);
058        if (t instanceof ArrayType) {
059            t = ((ArrayType) t).getBasicType();
060        }
061        return (t instanceof ObjectType) ? (ObjectType) t : null;
062    }
063
064
065    /**
066     * Call corresponding visitor method(s). The order is:
067     * Call visitor methods of implemented interfaces first, then
068     * call methods according to the class hierarchy in descending order,
069     * i.e., the most specific visitXXX() call comes last.
070     *
071     * @param v Visitor object
072     */
073    @Override
074    public void accept( final Visitor v ) {
075        v.visitLoadClass(this);
076        v.visitExceptionThrower(this);
077        v.visitStackProducer(this);
078        v.visitStackConsumer(this);
079        v.visitTypedInstruction(this);
080        v.visitCPInstruction(this);
081        v.visitCHECKCAST(this);
082    }
083}