What Is fop.jar? I got it from the fop-2.7-bin.zip.

fop.jar in fop-2.7-bin.zip is the JAR file for FOP 2.7, which is a print formatter driven by XSL formatting objects (XSL-FO). You can obtain fop.jar from the build folder of the fop-2.7-bin.zip file.

Below is the information about the fop.jar (2.2) file:

JAR File Size and Download Location:

JAR name: fop.jar, fop-2.7.jar
Target JDK version: 1.7
File name: fop.jar
File size: 4442817 bytes
Release date: 20-Jan-2022
Download: Apache FOP Website

Java source code files for fop.jar:

⏎ org/apache/fop/layoutmgr/KnuthElement.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.
 */

/* $Id: KnuthElement.java 893238 2009-12-22 17:20:51Z vhennebert $ */

package org.apache.fop.layoutmgr;

/**
 * This is the super class for KnuthBox, KnuthGlue and KnuthPenalty.
 *
 * It stores information common to all sub classes, and the methods to get it:
 * the width, a Position and a boolean marking KnuthElements used for some
 * special feature (for example, the additional elements used to represent
 * a space when text alignment is right, left or center).
 */
public abstract class KnuthElement extends ListElement {

    /** The value used as an infinite indicator. */
    public static final int INFINITE = 1000;

    private int width;
    private boolean auxiliary;

    /**
     * Creates a new <code>KnuthElement</code>.
     *
     * @param width    the width of this element
     * @param pos  the Position stored in this element
     * @param auxiliary is this an auxiliary element?
     */
    protected KnuthElement(int width, Position pos, boolean auxiliary) {
        super(pos);
        this.width = width;
        this.auxiliary = auxiliary;
    }

    /** @return true if this element is an auxiliary one. */
    public boolean isAuxiliary() {
        return auxiliary;
    }

    /** @return the width of this element. */
    public int getWidth() {
        return width;
    }

    /** @return the penalty value of this element, if applicable. */
    public int getPenalty() {
        throw new RuntimeException("Element is not a penalty");
    }

    /** @return the stretch value of this element, if applicable. */
    public int getStretch() {
        throw new RuntimeException("Element is not a glue");
    }

    /** @return the shrink value of this element, if applicable. */
    public int getShrink() {
        throw new RuntimeException("Element is not a glue");
    }

    /** {@inheritDoc} */
    public boolean isUnresolvedElement() {
        return false;
    }

}

⏎ org/apache/fop/layoutmgr/KnuthElement.java

Or download all of them as a single archive file:

File name: fop-2.7-src.zip
File size: 3401312 bytes
Release date: 2022-01-20
Download 

⇒ "fop" Command in fop-2.7-bin.zip

⇐ What Is fop-2.7-bin.zip

⇑ Download and Installing of FOP 2.x

⇑⇑ FAQ for FOP (Formatting Object Processor)