Nashorn in Java 15+

javax.script.ScriptEngineManager engineManager = new javax.script.ScriptEngineManager();
javax.script.ScriptEngineFactory engineFactory = new org.openjdk.nashorn.api.scripting.NashornScriptEngineFactory();

// Register Nashorn library
engineManager.registerEngineName("Nashorn", engineFactory);

javax.script.ScriptEngine engine = engineManager.getEngineByName("Nashorn");

// Run JavaScript code as usual
try {
    engine.eval("print('Hello World!');");

} catch (final javax.script.ScriptException ex) {
    ex.printStackTrace();
}