https://openjdk.java.net/ 
/*
 * Copyright (c) 2019, 2020, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.javadoc.internal.doclets.formats.html.markup;

import jdk.javadoc.internal.doclets.toolkit.Content;

import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;


Content for the <body> element. The content is a <div> element that contains a header that is always visible, and main content that can be scrolled if necessary. 
This is NOT part of any supported API.
 If you write code that depends on this, you do so at your own risk.
 This code and its internal interfaces are subject to change or
 deletion without notice.

/**
 * Content for the {@code <body>} element.
 *
 * The content is a {@code <div>} element that contains a
 * header that is always visible, and main content that
 * can be scrolled if necessary.
 *
 *  <p><b>This is NOT part of any supported API.
 *  If you write code that depends on this, you do so at your own risk.
 *  This code and its internal interfaces are subject to change or
 *  deletion without notice.</b>
 */
public class BodyContents extends Content {

    private List<Content> mainContents = new ArrayList<>();
    private HtmlTree header = null;
    private HtmlTree footer = null;

    public BodyContents addMainContent(Content content) {
        mainContents.add(content);
        return this;
    }

    public BodyContents setHeader(HtmlTree header) {
        this.header = Objects.requireNonNull(header);
        return this;
    }

    public BodyContents setFooter(HtmlTree footer) {
        this.footer = footer;
        return this;
    }

    
{@inheritDoc}

Implementation Requirements:This implementation always returns false.
Returns:false
/**
     * {@inheritDoc}
     *
     * @implSpec This implementation always returns {@code false}.
     *
     * @return {@code false}
     */
    @Override
    public boolean isEmpty() {
        return false;
    }

    @Override
    public boolean write(Writer out, boolean atNewline) throws IOException {
        return toContent().write(out, atNewline);
    }

    
Returns the HTML for the contents of the BODY element.

Returns:the HTML
/**
     * Returns the HTML for the contents of the BODY element.
     *
     * @return the HTML
     */
    private Content toContent() {
        if (header == null)
            throw new NullPointerException();

        HtmlTree flexHeader = header.addStyle(HtmlStyle.flexHeader);

        HtmlTree flexContent = HtmlTree.DIV(HtmlStyle.flexContent)
                .add(HtmlTree.MAIN().add(mainContents))
                .add(footer == null ? HtmlTree.EMPTY : footer);

        return HtmlTree.DIV(HtmlStyle.flexBox)
                .add(flexHeader)
                .add(flexContent);
    }
}