Apache BCEL Source Code Files are inside the Apache BCEL source package file like bcel-6.6.1-src.zip. Unzip the source package file and go to the "src/main" sub-directory, you will see source code files.

Here is the list of Java source code files of the Apache BCEL 6.6.1 in \Users\fyicenter\bcel-6.6.1\src:

⏎ org/apache/bcel/verifier/VerifierFactoryObserver.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.bcel.verifier;

/**
 * VerifierFactoryObserver instances are notified when new Verifier instances are created.
 *
 *
 * @see VerifierFactory#getVerifier(String)
 * @see VerifierFactory#getVerifiers()
 * @see VerifierFactory#attach(VerifierFactoryObserver)
 * @see VerifierFactory#detach(VerifierFactoryObserver)
 */
public interface VerifierFactoryObserver {

    /**
     * VerifierFactoryObserver instances are notified invoking this method. The String argument is the fully qualified class
     * name of a class a new Verifier instance created by the VerifierFactory operates on.
     */
    void update(String s);
}

⏎ org/apache/bcel/verifier/VerifierFactoryObserver.java

Or download all of them as a single archive file:

File name: bcel-6.6.1-sources.jar
File size: 688374 bytes
Release date: 2022-09-18
Download 

⇒ Install Apache BCEL 6.5.0 Binary Package

⇐ Download and Install Apache BCEL Source Package

⇑ Apache BCEL (Byte Code Engineering Library)

⇑⇑ Java Bytecode Tools