Apache BCEL Source Code Files are inside the Apache BCEL source package file like bcel-6.5.0-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 6.5.0 in \Users\fyicenter\bcel-6.5.0\src:

⏎ org/apache/bcel/generic/CPInstruction.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.generic;

import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantClass;
import org.apache.bcel.classfile.ConstantPool;
import org.apache.bcel.util.ByteSequence;

/**
 * Abstract super class for instructions that use an index into the
 * constant pool such as LDC, INVOKEVIRTUAL, etc.
 *
 * @see ConstantPoolGen
 * @see LDC
 * @see INVOKEVIRTUAL
 *
 */
public abstract class CPInstruction extends Instruction implements TypedInstruction,
        IndexedInstruction {

    /**
     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
     */
    @Deprecated
    protected int index; // index to constant pool


    /**
     * Empty constructor needed for Instruction.readInstruction.
     * Not to be used otherwise.
     */
    CPInstruction() {
    }


    /**
     * @param index to constant pool
     */
    protected CPInstruction(final short opcode, final int index) {
        super(opcode, (short) 3);
        setIndex(index);
    }


    /**
     * Dump instruction as byte code to stream out.
     * @param out Output stream
     */
    @Override
    public void dump( final DataOutputStream out ) throws IOException {
        out.writeByte(super.getOpcode());
        out.writeShort(index);
    }


    /**
     * Long output format:
     *
     * <name of opcode> "["<opcode number>"]"
     * "("<length of instruction>")" "<"< constant pool index>">"
     *
     * @param verbose long/short format switch
     * @return mnemonic for instruction
     */
    @Override
    public String toString( final boolean verbose ) {
        return super.toString(verbose) + " " + index;
    }


    /**
     * @return mnemonic for instruction with symbolic references resolved
     */
    @Override
    public String toString( final ConstantPool cp ) {
        final Constant c = cp.getConstant(index);
        String str = cp.constantToString(c);
        if (c instanceof ConstantClass) {
            str = str.replace('.', '/');
        }
        return org.apache.bcel.Const.getOpcodeName(super.getOpcode()) + " " + str;
    }


    /**
     * Read needed data (i.e., index) from file.
     * @param bytes input stream
     * @param wide wide prefix?
     */
    @Override
    protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
        setIndex(bytes.readUnsignedShort());
        super.setLength(3);
    }


    /**
     * @return index in constant pool referred by this instruction.
     */
    @Override
    public final int getIndex() {
        return index;
    }


    /**
     * Set the index to constant pool.
     * @param index in  constant pool.
     */
    @Override
    public void setIndex( final int index ) { // TODO could be package-protected?
        if (index < 0) {
            throw new ClassGenException("Negative index value: " + index);
        }
        this.index = index;
    }


    /** @return type related with this instruction.
     */
    @Override
    public Type getType( final ConstantPoolGen cpg ) {
        final ConstantPool cp = cpg.getConstantPool();
        String name = cp.getConstantString(index, org.apache.bcel.Const.CONSTANT_Class);
        if (!name.startsWith("[")) {
            name = "L" + name + ";";
        }
        return Type.getType(name);
    }
}

⏎ org/apache/bcel/generic/CPInstruction.java

Or download all of them as a single archive file:

File name: bcel-6.5.0-fyi.zip
File size: 706792 bytes
Release date: 2020-07-03
Download 

⇒ JDK "javap" Command

⇐ Install Apache BCEL 6.5.0 Binary Package

⇑ Apache BCEL (Byte Code Engineering Library)

⇑⇑ Java Bytecode Tools