How to convert Jira's wiki markup to HTML from Java

Forge Forge Platform and Tools
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com.atlassian.renderer atlassian-renderer 9.0.1

package com.example.demo;

import com.atlassian.renderer.RenderContext;
import com.atlassian.renderer.wysiwyg.converter.DefaultWysiwygConverter;

public class WikiMarkupToHtml {

public void convert() {
	String wikiText1 = "* Java\n* Python"; // Wiki-style
	String wikiText2 = "<ul><li>Java</li><li>Python</li></ul>"; // HTML-style

	DefaultWysiwygConverter converter = new DefaultWysiwygConverter();

	try {
		RenderContext context = new RenderContext();
		// Convert Wiki Markup to HTML
		String html = converter.convertWikiMarkupToXHtml(context, wikiText1);

		// Convert HTML to Wiki Markup
		String wiki = converter.convertXHtmlToWikiMarkup(wikiText2);

		System.out.println("Wiki Markup ➡️ HTML:\n" + html);
		System.out.println("\nHTML ➡️ Wiki Markup:\n" + wiki);
	} catch (Exception e) {
		e.printStackTrace();
	}
}

public static void main(String[] args) {
	WikiMarkupToHtml demo = new WikiMarkupToHtml();
	demo.convert();
}

}

Can help me
java.lang.NullPointerException: Cannot invoke “com.atlassian.renderer.WikiStyleRenderer.convertWikiToXHtml(com.atlassian.renderer.RenderContext, String)” because “this.renderer” is null
at com.atlassian.renderer.wysiwyg.converter.DefaultWysiwygConverter.convertWikiMarkupToXHtml(DefaultWysiwygConverter.java:406)
at com.example.demo.WikiMarkupToHtml.convert(WikiMarkupToHtml.java:17)
at com.example.demo.WikiMarkupToHtml.main(WikiMarkupToHtml.java:31)