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/generic/IINC.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.Const;
import org.apache.bcel.util.ByteSequence;

/**
 * IINC - Increment local variable by constant
 */
public class IINC extends LocalVariableInstruction {

    private boolean wide;
    private int c;

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

    /**
     * @param n index of local variable
     * @param c increment factor
     */
    public IINC(final int n, final int c) {
        // Default behavior of LocalVariableInstruction causes error
        super.setOpcode(Const.IINC);
        super.setLength((short) 3);
        setIndex(n); // May set wide as side effect
        setIncrement(c);
    }

    /**
     * Calls corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
     *
     * @param v Visitor object
     */
    @Override
    public void accept(final Visitor v) {
        v.visitLocalVariableInstruction(this);
        v.visitIINC(this);
    }

    /**
     * Dumps instruction as byte code to stream out.
     *
     * @param out Output stream
     */
    @Override
    public void dump(final DataOutputStream out) throws IOException {
        if (wide) {
            out.writeByte(Const.WIDE);
        }
        out.writeByte(super.getOpcode());
        if (wide) {
            out.writeShort(super.getIndex());
            out.writeShort(c);
        } else {
            out.writeByte(super.getIndex());
            out.writeByte(c);
        }
    }

    /**
     * @return increment factor
     */
    public final int getIncrement() {
        return c;
    }

    /**
     * @return int type
     */
    @Override
    public Type getType(final ConstantPoolGen cp) {
        return Type.INT;
    }

    /**
     * Reads needed data (e.g. index) from file.
     */
    @Override
    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
        this.wide = wide;
        if (wide) {
            super.setLength(6);
            super.setIndexOnly(bytes.readUnsignedShort());
            c = bytes.readShort();
        } else {
            super.setLength(3);
            super.setIndexOnly(bytes.readUnsignedByte());
            c = bytes.readByte();
        }
    }

    /**
     * Sets increment factor.
     */
    public final void setIncrement(final int c) {
        this.c = c;
        setWide();
    }

    /**
     * Sets index of local variable.
     */
    @Override
    public final void setIndex(final int n) {
        if (n < 0) {
            throw new ClassGenException("Negative index value: " + n);
        }
        super.setIndexOnly(n);
        setWide();
    }

    private void setWide() {
        wide = super.getIndex() > Const.MAX_BYTE;
        if (c > 0) {
            wide = wide || c > Byte.MAX_VALUE;
        } else {
            wide = wide || c < Byte.MIN_VALUE;
        }
        if (wide) {
            super.setLength(6); // wide byte included
        } else {
            super.setLength(3);
        }
    }

    /**
     * Returns mnemonic for instruction.
     *
     * @return mnemonic for instruction.
     */
    @Override
    public String toString(final boolean verbose) {
        return super.toString(verbose) + " " + c;
    }
}

⏎ org/apache/bcel/generic/IINC.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