itextpdf.jar is a component in iText 5 Java library to provide core functionalities. iText Java library allows you to generate and manage PDF documents.

The Source Code files are provided at iText GitHub site.

You can compile it to generate your JAR file, using pom.xml as the build configuration file.

The source code of itextpdf-5.5.14.jar is provided below:

⏎ com/itextpdf/text/pdf/PdfLayer.java

/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2020 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf;

import java.io.IOException;
import java.util.ArrayList;

import com.itextpdf.text.error_messages.MessageLocalization;
/**
 * An optional content group is a dictionary representing a collection of graphics
 * that can be made visible or invisible dynamically by users of viewer applications.
 * In iText they are referenced as layers.
 *
 * @author Paulo Soares
 */
public class PdfLayer extends PdfDictionary implements PdfOCG {
    protected PdfIndirectReference ref;
    protected ArrayList<PdfLayer> children;
    protected PdfLayer parent;
    protected String title;

    /**
     * Holds value of property on.
     */
    private boolean on = true;

    /**
     * Holds value of property onPanel.
     */
    private boolean onPanel = true;

    PdfLayer(String title) {
        this.title = title;
    }

    /**
     * Creates a title layer. A title layer is not really a layer but a collection of layers
     * under the same title heading.
     * @param title the title text
     * @param writer the <CODE>PdfWriter</CODE>
     * @return the title layer
     */
    public static PdfLayer createTitle(String title, PdfWriter writer) {
        if (title == null)
            throw new NullPointerException(MessageLocalization.getComposedMessage("title.cannot.be.null"));
        PdfLayer layer = new PdfLayer(title);
        writer.registerLayer(layer);
        return layer;
    }
    /**
     * Creates a new layer.
     * @param name the name of the layer
     * @param writer the writer
     * @throws IOException 
     */
    public PdfLayer(String name, PdfWriter writer) throws IOException {
        super(PdfName.OCG);
        setName(name);
        if (writer instanceof PdfStamperImp)
        	ref = writer.addToBody(this).getIndirectReference();
        else
        	ref = writer.getPdfIndirectReference();
        writer.registerLayer(this);
    }

    String getTitle() {
        return title;
    }

    /**
     * Adds a child layer. Nested layers can only have one parent.
     * @param child the child layer
     */
    public void addChild(PdfLayer child) {
        if (child.parent != null)
            throw new IllegalArgumentException(MessageLocalization.getComposedMessage("the.layer.1.already.has.a.parent", child.getAsString(PdfName.NAME).toUnicodeString()));
        child.parent = this;
        if (children == null)
            children = new ArrayList<PdfLayer>();
        children.add(child);
    }


    /**
     * Gets the parent layer.
     * @return the parent layer or <CODE>null</CODE> if the layer has no parent
     */
    public PdfLayer getParent() {
        return parent;
    }

    /**
     * Gets the children layers.
     * @return the children layers or <CODE>null</CODE> if the layer has no children
     */
    public ArrayList<PdfLayer> getChildren() {
        return children;
    }

    /**
     * Gets the <CODE>PdfIndirectReference</CODE> that represents this layer.
     * @return the <CODE>PdfIndirectReference</CODE> that represents this layer
     */
    public PdfIndirectReference getRef() {
        return ref;
    }

    /**
     * Sets the <CODE>PdfIndirectReference</CODE> that represents this layer.
     * This can only be done from PdfStamperImp.
     * @param	ref	The reference to the OCG object
     * @since	2.1.2
     */
    void setRef(PdfIndirectReference ref) {
    	this.ref = ref;
    }

    /**
     * Sets the name of this layer.
     * @param name the name of this layer
     */
    public void setName(String name) {
        put(PdfName.NAME, new PdfString(name, PdfObject.TEXT_UNICODE));
    }

    /**
     * Gets the dictionary representing the layer. It just returns <CODE>this</CODE>.
     * @return the dictionary representing the layer
     */
    public PdfObject getPdfObject() {
        return this;
    }

    /**
     * Gets the initial visibility of the layer.
     * @return the initial visibility of the layer
     */
    public boolean isOn() {
        return this.on;
    }

    /**
     * Sets the initial visibility of the layer.
     * @param on the initial visibility of the layer
     */
    public void setOn(boolean on) {
        this.on = on;
    }

    private PdfDictionary getUsage() {
        PdfDictionary usage = getAsDict(PdfName.USAGE);
        if (usage == null) {
            usage = new PdfDictionary();
            put(PdfName.USAGE, usage);
        }
        return usage;
    }

    /**
     * Used by the creating application to store application-specific
     * data associated with this optional content group.
     * @param creator a text string specifying the application that created the group
     * @param subtype a string defining the type of content controlled by the group. Suggested
     * values include but are not limited to <B>Artwork</B>, for graphic-design or publishing
     * applications, and <B>Technical</B>, for technical designs such as building plans or
     * schematics
     */
    public void setCreatorInfo(String creator, String subtype) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.CREATOR, new PdfString(creator, PdfObject.TEXT_UNICODE));
        dic.put(PdfName.SUBTYPE, new PdfName(subtype));
        usage.put(PdfName.CREATORINFO, dic);
    }

    /**
     * Specifies the language of the content controlled by this
     * optional content group
     * @param lang a language string which specifies a language and possibly a locale
     * (for example, <B>es-MX</B> represents Mexican Spanish)
     * @param preferred used by viewer applications when there is a partial match but no exact
     * match between the system language and the language strings in all usage dictionaries
     */
    public void setLanguage(String lang, boolean preferred) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.LANG, new PdfString(lang, PdfObject.TEXT_UNICODE));
        if (preferred)
            dic.put(PdfName.PREFERRED, PdfName.ON);
        usage.put(PdfName.LANGUAGE, dic);
    }

    /**
     * Specifies the recommended state for content in this
     * group when the document (or part of it) is saved by a viewer application to a format
     * that does not support optional content (for example, an earlier version of
     * PDF or a raster image format).
     * @param export the export state
     */
    public void setExport(boolean export) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.EXPORTSTATE, export ? PdfName.ON : PdfName.OFF);
        usage.put(PdfName.EXPORT, dic);
    }

    /**
     * Specifies a range of magnifications at which the content
     * in this optional content group is best viewed.
     * @param min the minimum recommended magnification factors at which the group
     * should be ON. A negative value will set the default to 0
     * @param max the maximum recommended magnification factor at which the group
     * should be ON. A negative value will set the largest possible magnification supported by the
     * viewer application
     */
    public void setZoom(float min, float max) {
        if (min <= 0 && max < 0)
            return;
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        if (min > 0)
            dic.put(PdfName.MIN_LOWER_CASE, new PdfNumber(min));
        if (max >= 0)
            dic.put(PdfName.MAX_LOWER_CASE, new PdfNumber(max));
        usage.put(PdfName.ZOOM, dic);
    }

    /**
     * Specifies that the content in this group is intended for
     * use in printing
     * @param subtype a name specifying the kind of content controlled by the group;
     * for example, <B>Trapping</B>, <B>PrintersMarks</B> and <B>Watermark</B>
     * @param printstate indicates that the group should be
     * set to that state when the document is printed from a viewer application
     */
    public void setPrint(String subtype, boolean printstate) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.SUBTYPE, new PdfName(subtype));
        dic.put(PdfName.PRINTSTATE, printstate ? PdfName.ON : PdfName.OFF);
        usage.put(PdfName.PRINT, dic);
    }

    /**
     * Indicates that the group should be set to that state when the
     * document is opened in a viewer application.
     * @param view the view state
     */
    public void setView(boolean view) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.VIEWSTATE, view ? PdfName.ON : PdfName.OFF);
        usage.put(PdfName.VIEW, dic);
    }
    
    /**
     * Indicates that the group contains a pagination artifact.
     * @param pe one of the following names: "HF" (Header Footer),
     * "FG" (Foreground), "BG" (Background), or "L" (Logo).
     * @since 5.0.2
     */
    public void setPageElement(String pe) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.SUBTYPE, new PdfName(pe));
        usage.put(PdfName.PAGEELEMENT, dic);
    }
    
    /**
     * One of more users for whom this optional content group is primarily intended.
     * @param type should be "Ind" (Individual), "Ttl" (Title), or "Org" (Organization).
     * @param names one or more names
     * @since 5.0.2
     */
    public void setUser(String type, String... names) {
        PdfDictionary usage = getUsage();
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.TYPE, new PdfName(type));
        PdfArray arr = new PdfArray();
        for (String s : names)
        	arr.add(new PdfString(s, PdfObject.TEXT_UNICODE));
        usage.put(PdfName.NAME, arr);
        usage.put(PdfName.USER, dic);
    }

    /**
     * Gets the layer visibility in Acrobat's layer panel
     * @return the layer visibility in Acrobat's layer panel
     */
    public boolean isOnPanel() {
        return this.onPanel;
    }

    /**
     * Sets the visibility of the layer in Acrobat's layer panel. If <CODE>false</CODE>
     * the layer cannot be directly manipulated by the user. Note that any children layers will
     * also be absent from the panel.
     * @param onPanel the visibility of the layer in Acrobat's layer panel
     */
    public void setOnPanel(boolean onPanel) {
        this.onPanel = onPanel;
    }

}

⏎ com/itextpdf/text/pdf/PdfLayer.java

Or download all of them as a single archive file:

File name: itextpdf-5.5.14-fyi.zip
File size: 2163839 bytes
Release date: 2009-10-09
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⇒ iText-2.1.6.jar - iText, a JAVA-PDF library

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⇑⇑ iText for PDF Generation