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/Repository.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;

import java.io.IOException;

import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.util.ClassPath;
import org.apache.bcel.util.SyntheticRepository;

/**
 * The repository maintains informations about class interdependencies, e.g., whether a class is a sub-class of another.
 * Delegates actual class loading to SyntheticRepository with current class path by default.
 *
 * @see org.apache.bcel.util.Repository
 * @see SyntheticRepository
 */
public abstract class Repository {

    private static org.apache.bcel.util.Repository repository = SyntheticRepository.getInstance();

    /**
     * Adds clazz to repository if there isn't an equally named class already in there.
     *
     * @return old entry in repository
     */
    public static JavaClass addClass(final JavaClass clazz) {
        final JavaClass old = repository.findClass(clazz.getClassName());
        repository.storeClass(clazz);
        return old;
    }

    /**
     * Clears the repository.
     */
    public static void clearCache() {
        repository.clear();
    }

    /**
     * @return all interfaces implemented by class and its super classes and the interfaces that those interfaces extend,
     *         and so on. (Some people call this a transitive hull).
     * @throws ClassNotFoundException if any of the class's superclasses or superinterfaces can't be found
     */
    public static JavaClass[] getInterfaces(final JavaClass clazz) throws ClassNotFoundException {
        return clazz.getAllInterfaces();
    }

    /**
     * @return all interfaces implemented by class and its super classes and the interfaces that extend those interfaces,
     *         and so on
     * @throws ClassNotFoundException if the named class can't be found, or if any of its superclasses or superinterfaces
     *         can't be found
     */
    public static JavaClass[] getInterfaces(final String className) throws ClassNotFoundException {
        return getInterfaces(lookupClass(className));
    }

    /**
     * @return currently used repository instance
     */
    public static org.apache.bcel.util.Repository getRepository() {
        return repository;
    }

    /**
     * @return list of super classes of clazz in ascending order, i.e., Object is always the last element
     * @throws ClassNotFoundException if any of the superclasses can't be found
     */
    public static JavaClass[] getSuperClasses(final JavaClass clazz) throws ClassNotFoundException {
        return clazz.getSuperClasses();
    }

    /**
     * @return list of super classes of clazz in ascending order, i.e., Object is always the last element.
     * @throws ClassNotFoundException if the named class or any of its superclasses can't be found
     */
    public static JavaClass[] getSuperClasses(final String className) throws ClassNotFoundException {
        return getSuperClasses(lookupClass(className));
    }

    /**
     * @return true, if clazz is an implementation of interface inter
     * @throws ClassNotFoundException if any superclasses or superinterfaces of clazz can't be found
     */
    public static boolean implementationOf(final JavaClass clazz, final JavaClass inter) throws ClassNotFoundException {
        return clazz.implementationOf(inter);
    }

    /**
     * @return true, if clazz is an implementation of interface inter
     * @throws ClassNotFoundException if inter or any superclasses or superinterfaces of clazz can't be found
     */
    public static boolean implementationOf(final JavaClass clazz, final String inter) throws ClassNotFoundException {
        return implementationOf(clazz, lookupClass(inter));
    }

    /**
     * @return true, if clazz is an implementation of interface inter
     * @throws ClassNotFoundException if clazz or any superclasses or superinterfaces of clazz can't be found
     */
    public static boolean implementationOf(final String clazz, final JavaClass inter) throws ClassNotFoundException {
        return implementationOf(lookupClass(clazz), inter);
    }

    /**
     * @return true, if clazz is an implementation of interface inter
     * @throws ClassNotFoundException if clazz, inter, or any superclasses or superinterfaces of clazz can't be found
     */
    public static boolean implementationOf(final String clazz, final String inter) throws ClassNotFoundException {
        return implementationOf(lookupClass(clazz), lookupClass(inter));
    }

    /**
     * Equivalent to runtime "instanceof" operator.
     *
     * @return true, if clazz is an instance of superclass
     * @throws ClassNotFoundException if any superclasses or superinterfaces of clazz can't be found
     */
    public static boolean instanceOf(final JavaClass clazz, final JavaClass superclass) throws ClassNotFoundException {
        return clazz.instanceOf(superclass);
    }

    /**
     * @return true, if clazz is an instance of superclass
     * @throws ClassNotFoundException if superclass can't be found
     */
    public static boolean instanceOf(final JavaClass clazz, final String superclass) throws ClassNotFoundException {
        return instanceOf(clazz, lookupClass(superclass));
    }

    /**
     * @return true, if clazz is an instance of superclass
     * @throws ClassNotFoundException if clazz can't be found
     */
    public static boolean instanceOf(final String clazz, final JavaClass superclass) throws ClassNotFoundException {
        return instanceOf(lookupClass(clazz), superclass);
    }

    /**
     * @return true, if clazz is an instance of superclass
     * @throws ClassNotFoundException if either clazz or superclass can't be found
     */
    public static boolean instanceOf(final String clazz, final String superclass) throws ClassNotFoundException {
        return instanceOf(lookupClass(clazz), lookupClass(superclass));
    }

    /**
     * Tries to find class source using the internal repository instance.
     *
     * @see Class
     * @return JavaClass object for given runtime class
     * @throws ClassNotFoundException if the class could not be found or parsed correctly
     */
    public static JavaClass lookupClass(final Class<?> clazz) throws ClassNotFoundException {
        return repository.loadClass(clazz);
    }

    /**
     * Lookups class somewhere found on your CLASSPATH, or whereever the repository instance looks for it.
     *
     * @return class object for given fully qualified class name
     * @throws ClassNotFoundException if the class could not be found or parsed correctly
     */
    public static JavaClass lookupClass(final String className) throws ClassNotFoundException {
        return repository.loadClass(className);
    }

    /**
     * @return class file object for given Java class by looking on the system class path; returns null if the class file
     *         can't be found
     */
    public static ClassPath.ClassFile lookupClassFile(final String className) {
        try (ClassPath path = repository.getClassPath()) {
            if (path == null) {
                return null;
            }
            return path.getClassFile(className);
        } catch (final IOException e) {
            return null;
        }
    }

    /**
     * Removes given class from repository.
     */
    public static void removeClass(final JavaClass clazz) {
        repository.removeClass(clazz);
    }

    /**
     * Removes class with given (fully qualified) name from repository.
     */
    public static void removeClass(final String clazz) {
        repository.removeClass(repository.findClass(clazz));
    }

    /**
     * Sets repository instance to be used for class loading
     */
    public static void setRepository(final org.apache.bcel.util.Repository rep) {
        repository = rep;
    }
}

⏎ org/apache/bcel/Repository.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