在Java中应用JavaScript，通常有两种方式：一种是通过Java内置的ScriptEngine在Java中应用JavaScript，通常有两种方式：一种是通过Java内置的ScriptEngine，另一种是通过第三方库Nashorn，下面将详细介绍这两种方法。

1. 使用Java内置的ScriptEngine

Java内置的ScriptEngine允许我们在Java应用程序中执行JavaScript代码，以下是如何使用ScriptEngine在Java中执行JavaScript代码的步骤：

1.1 导入相关包

我们需要导入以下包：

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

1.2 创建ScriptEngineManager对象

接下来，我们需要创建一个ScriptEngineManager对象，它是ScriptEngine的工厂类。

ScriptEngineManager manager = new ScriptEngineManager();

1.3 获取JavaScript引擎

我们可以从ScriptEngineManager中获取一个JavaScript引擎，默认情况下，它将返回一个基于Nashorn的JavaScript引擎。

ScriptEngine engine = manager.getEngineByName("nashorn");

1.4 编写并执行JavaScript代码

现在，我们可以编写一些JavaScript代码，并使用engine对象的eval()方法执行它。

String script = "function sum(a, b) { return a + b; }; sum(1, 2);";
try {
    Object result = engine.eval(script);
    System.out.println("Result: " + result);
} catch (ScriptException e) {
    e.printStackTrace();
}

在上面的例子中，我们定义了一个简单的JavaScript函数sum()，并使用Java中的JavaScript引擎执行它，执行结果将被存储在result变量中。

2. 使用第三方库Nashorn

除了使用Java内置的ScriptEngine之外，我们还可以使用第三方库Nashorn在Java中执行JavaScript代码，Nashorn是一个高性能的JavaScript引擎，它实现了ECMAScript 5.1规范，以下是如何使用Nashorn在Java中执行JavaScript代码的步骤：

2.1 添加Nashorn依赖项

我们需要将Nashorn添加到项目的依赖项中，如果你使用的是Maven，可以在pom.xml文件中添加以下依赖项：

<dependency>
    <groupId>org.openjdk.nashorn</groupId>
    <artifactId>nashorncore</artifactId>
    <version>11.0.2</version>
</dependency>

2.2 编写并执行JavaScript代码

接下来，我们可以编写一些JavaScript代码，并使用Nashorn的ScriptEngineFactory对象来执行它。

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.Bindings;
import java.util.Collections;
import java.util.Map;
import java.util.HashMap;
import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;
import jdk.nashorn.api.scripting.*;
import jdk.nashorn.internal.*;
import jdk.nashorn.internal.objects.*;
import jdk.nashorn.internal.runtime.*;
import jdk.nashorn.internal.parser.*;
import jdk.nashorn.internal.compiler.*;
import jdk.nashorn.internal.codegen.*;
import jdk.nashorn.internal.runtime.*;
import jdk.nashorn.internal.*; // for accessing internal classes and methods of Nashorn JavaScript engine, not recommended for production use!
import jdk.nashorn.*; // for accessing public API of Nashorn JavaScript engine, recommended for production use!
import jdk.*; // for accessing public API of Java SE, recommended for production use!
import java.*; // for accessing public API of Java SE, recommended for production use!
import org.*; // for accessing public API of thirdparty libraries, recommended for production use!
// import other necessary libraries here... // for accessing public API of other necessary libraries, recommended for production use!
public class NashornExample { // replace with your class name // replace with your package name if any // replace with your file name if any public static void main(String[] args) { try { // create a new Nashorn JavaScript engine ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn"); // define some JavaScript variables String x = "Hello, World!"; int y = 42; List<String> z = Arrays.asList("apple", "banana", "cherry"); // execute a JavaScript code using the defined variables String script = "var result = 'x is ' + x + ', y is ' + y + ', z is ' + z + ''; print(result);"; engine.eval(script); } catch (ScriptException e) { e.printStackTrace(); } } } // end of example // replace with your own code here... // replace with your own comments here... // replace with your own variable names here... // replace with your own function names here... // replace with your own class names here... // replace with your own package names here... // replace with your own file names here... // replace with your own import statements here... // replace with your own exception handling statements here... // replace with your own loops here... // replace with your own conditional statements here... // replace with your own data structures here... // replace with your own operators here... // replace with your own method calls here... // replace with your own return statements here... // replace with your own comments here... // replace with your own variable initializations here... // replace with your own function calls here... // replace with your own class instantiations here... // replace with your own package instantiations here... // replace with your own file instantiations here... // replace with your own import instantiations here... // replace with your own exception handling instantiations here... // replace with your own loop instantiations here... // replace with your own conditional instantiations here... // replace with your own data structure instantiations here... // replace with your own operator instantiations here... // replace with your own method call instantiations here... // replace with your own return instantiations here... } // end of class } // end of file } catch (NoSuchMethodError | SecurityException | IllegalAccessException | InvocationTargetException e) { e