Java反射基础

Java

后端

发布日期: 2018-11-07

一、概述

1. 简介

Java反射(Reflection)机制就是在运行状态中，对于任意一个类，都能够知道这个类的属性和方法。对于任意一个对象能够调用它的任意一个属性和方法。这种动态获取的信息和动态调用对象的方法的功能称为Java语言的反射机制。Java程序中一般的对象的类型都是在编译期就确定下来的，而Java反射机制可以动态地创建对象并调用其属性，这样的对象的类型在编译期是未知的。所以我们可以通过反射机制直接创建对象，即使这个对象的类型在编译期是未知的。

反射的核心是JVM在运行时才动态加载类或调用方法/访问属性，它不需要事先（写代码的时候或编译期）知道运行对象是谁。反射机制就是通过java.lang.Class类来实现的，在Java中，Object 类是所有类的根类，而Class类就是描述Java类的类。

注：因为Class类也是类，所以Object也包括Class类。

2. 主要功能

Java反射框架主要提供以下功能：

在运行时判断任意一个对象所属的类；
在运行时构造任意一个类的对象；
在运行时判断任意一个类所具有的成员变量和方法（通过反射甚至可以调用private方法）；
在运行时调用任意一个对象的方法；
修改构造函数、方法、属性的可见性。

3. 主要用途

反射最重要的用途就是开发各种通用框架。很多框架（比如Spring）都是配置化的（比如通过XML文件配置JavaBean,Action之类的），为了保证框架的通用性，它们可能需要根据配置文件加载不同的对象或类，调用不同的方法，这个时候就必须用到反射——运行时动态加载需要加载的对象。对与框架开发人员来说，反射虽小但作用非常大，它是各种容器实现的核心。

二、反射的使用

1. 获取Class对象

反射的各种功能都需要通过Class对象来实现，因此，需要知道如何获取Class对象，主要有以下几种方式。

使用 Class.forName() 的静态方法

Class.forName(String className)方法可以通过类或接口的名称（一个字符串或完全限定名）来获取对应的Class对象。

Class<?> cls = Class.forName("com.zxd.Zealot");

直接获取某个类的class(最安全/性能最好)

Class<String> cls = String.class;

调用某个对象的 getClass() 方法

Class<String> cls = str.getClass();

2. 判断是否为某个类的实例

一般地，我们用instanceof关键字来判断是否为某个类的实例。同时我们也可以借助反射中Class对象的isInstance()方法来判断是否为某个类的实例，它是一个Native方法：

public native boolean isInstance(Object obj);

3. 创建实例

通过反射来生成对象主要有两种方式。

使用Class对象的newInstance()方法

Class<?> c = String.class;
Object str = c.newInstance();

通过Class对象获取指定的Constructor对象，再调用Constructor对象的newInstance()方法

// 获取String所对应的Class对象
Class<?> c = String.class;
// 获取String类带一个String参数的构造器
Constructor constructor = c.getConstructor(String.class);
// 根据构造器创建实例
Object obj = constructor.newInstance("23333");
System.out.println(obj);

注：这种方法可以用指定的构造器构造类的实例。

4. 获取方法

获取某个Class对象的方法集合，主要有以下几个方法：

getDeclaredMethods()方法返回类或接口声明的所有方法，包括公共、保护、默认（包）访问和私有方法，但不包括继承的方法。

public Method[] getDeclaredMethods() throws SecurityException

getMethods()方法返回某个类的所有公用（public）方法，包括其继承类的公用方法。

public Method[] getMethods() throws SecurityException

getMethod()方法返回一个特定的方法，其中第一个参数为方法名称，后面的参数为方法的参数对应Class的对象。

public Method getMethod(String name, Class<?>... parameterTypes)

代码示例：

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Test {
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">test</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">IllegalAccessException</span><span class="token punctuation">,</span>
        <span class="token class-name">InstantiationException</span><span class="token punctuation">,</span> <span class="token class-name">NoSuchMethodException</span><span class="token punctuation">,</span> <span class="token class-name">InvocationTargetException</span> <span class="token punctuation">&#123;</span>
    <span class="token class-name">Class</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token operator">?</span><span class="token punctuation">></span></span> c <span class="token operator">=</span> <span class="token class-name">MethodClass</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">;</span>
    <span class="token class-name">Object</span> object <span class="token operator">=</span> c<span class="token punctuation">.</span><span class="token function">newInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Method</span><span class="token punctuation">[</span><span class="token punctuation">]</span> methods <span class="token operator">=</span> c<span class="token punctuation">.</span><span class="token function">getMethods</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Method</span><span class="token punctuation">[</span><span class="token punctuation">]</span> declaredMethods <span class="token operator">=</span> c<span class="token punctuation">.</span><span class="token function">getDeclaredMethods</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">//获取MethodClass类的add方法</span>
    <span class="token class-name">Method</span> method <span class="token operator">=</span> c<span class="token punctuation">.</span><span class="token function">getMethod</span><span class="token punctuation">(</span><span class="token string">"add"</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//getMethods()方法获取的所有方法</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"getMethods获取的方法："</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token class-name">Method</span> m<span class="token operator">:</span> methods<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>m<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>

    <span class="token comment">//getDeclaredMethods()方法获取的所有方法</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"getDeclaredMethods获取的方法："</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">for</span><span class="token punctuation">(</span><span class="token class-name">Method</span> m<span class="token operator">:</span> declaredMethods<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>m<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

}
class MethodClass {
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">int</span> fuck <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">add</span><span class="token punctuation">(</span><span class="token keyword">int</span> a<span class="token punctuation">,</span> <span class="token keyword">int</span> b<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> a <span class="token operator">+</span> b<span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">sub</span><span class="token punctuation">(</span><span class="token keyword">int</span> a<span class="token punctuation">,</span> <span class="token keyword">int</span> b<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> a <span class="token operator">-</span> b<span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

}

注：通过getMethods()获取的方法可以获取到父类的方法,比如java.lang.Object下定义的各个方法。

5. 获取构造方法

获取类构造器的用法与上述获取方法的用法类似。主要是通过Class类的getConstructor方法得到Constructor类的一个实例，而Constructor类有一个newInstance方法可以创建一个对象实例:

public T newInstance(Object ... initargs)

注：此方法可以根据传入的参数来调用对应的Constructor创建对象实例。

6. 获取类的成员变量信息

获取的方法同Method相似，主要是这几个方法，在此不再赘述：

Field getField(String name): 访问公有的成员变量。
Field[] getDeclaredFields()：所有已声明的成员变量。但不能得到其父类的成员变量。
Field[] getFields()和Field[] getDeclaredFields()用法同上。

7. 调用方法

当我们从类中获取了一个方法后，我们就可以用invoke()方法来调用这个方法。invoke方法的原型为:

public Object invoke(Object obj, Object... args) throws IllegalAccessException, IllegalArgumentException,
 InvocationTargetException

代码示例：

public class Test {

<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> args<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">IllegalAccessException</span><span class="token punctuation">,</span>
        <span class="token class-name">InstantiationException</span><span class="token punctuation">,</span> <span class="token class-name">NoSuchMethodException</span><span class="token punctuation">,</span> <span class="token class-name">InvocationTargetException</span> <span class="token punctuation">&#123;</span>
    <span class="token class-name">Class</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token operator">?</span><span class="token punctuation">></span></span> klass <span class="token operator">=</span> <span class="token class-name">MethodClass</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">;</span>
    <span class="token comment">//创建 MethodClass 的实例</span>
    <span class="token class-name">Object</span> obj <span class="token operator">=</span> klass<span class="token punctuation">.</span><span class="token function">newInstance</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">//获取 MethodClass 类的add方法</span>
    <span class="token class-name">Method</span> method <span class="token operator">=</span> klass<span class="token punctuation">.</span><span class="token function">getMethod</span><span class="token punctuation">(</span><span class="token string">"add"</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">,</span> <span class="token keyword">int</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">//调用 method 对应的方法 => add(1,4)</span>
    <span class="token class-name">Object</span> result <span class="token operator">=</span> method<span class="token punctuation">.</span><span class="token function">invoke</span><span class="token punctuation">(</span>obj<span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>result<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

}
class MethodClass {
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">int</span> fuck <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">add</span><span class="token punctuation">(</span><span class="token keyword">int</span> a<span class="token punctuation">,</span> <span class="token keyword">int</span> b<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> a <span class="token operator">+</span> b<span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">sub</span><span class="token punctuation">(</span><span class="token keyword">int</span> a<span class="token punctuation">,</span> <span class="token keyword">int</span> b<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> a <span class="token operator">-</span> b<span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

}

8. 利用反射创建数组

数组在Java里是比较特殊的一种类型，它可以赋值给一个Object Reference。下面我们看一看利用反射创建数组的例子：

public static void testArray() throws ClassNotFoundException {
    // 使用`java.lang.reflect.Array`反射创建长度为25的字符串数组.
    Class<?> cls = Class.forName("java.lang.String");
    Object array = Array.newInstance(cls, 25);
    // 往数组里添加内容
    Array.set(array,0, "hello");
    Array.set(array,1, "Java");
    Array.set(array,2, "Go");
    Array.set(array,3, "Scala");
    Array.set(array,4, "Clojure");
    // 获取某一项的内容
    System.out.println(Array.get(array, 3));
}

三、使用反射获取信息

Class类提供了大量的实例方法来获取该Class对象所对应的详细信息，Class类大致包含如下方法，其中每个方法都包含多个重载版本，因此我们只是做简单的介绍，详细请参考JDK文档。

1. 获取类内信息

构造器: Constructor<T> getConstructor(Class<?>... parameterTypes)
包含的方法: Method getMethod(String name, Class<?>... parameterTypes)
包含的属性: Field getField(String name)
包含的Annotation: <A extends Annotation> A getAnnotation(Class<A> annotationClass)
内部类: Class<?>[] getDeclaredClasses()
外部类: Class<?> getDeclaringClass()
所实现的接口: Class<?>[] getInterfaces()
修饰符: int getModifiers()
所在包: Package getPackage()
类名: String getName()
简称: String getSimpleName()

2. 判断类本身信息的方法

是否注解类型: boolean isAnnotation()
是否使用了该Annotation修饰: boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
是否匿名类: boolean isAnonymousClass()
是否数组: boolean isArray()
是否枚举: boolean isEnum()
是否原始类型: boolean isPrimitive()
是否接口: boolean isInterface()
obj是否是该Class的实例: boolean isInstance(Object obj)

3. 使用反射获取泛型信息

为了通过反射操作泛型以迎合实际开发的需要, Java新增了java.lang.reflect.ParameterizedType、java.lang.reflect.GenericArrayType、java.lang.reflect.TypeVariable、java.lang.reflect.WildcardType几种类型来代表不能归一到Class类型但是又和原始类型同样重要的类型。

ParameterizedType: 一种参数化类型, 比如Collection
GenericArrayType: 一种元素类型是参数化类型或者类型变量的数组类型
TypeVariable: 各种类型变量的公共接口
WildcardType: 一种通配符类型表达式, 如?、? extends Number、? super Integer

代码示例：

public class Client {

<span class="token keyword">private</span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">Object</span><span class="token punctuation">></span></span> objectMap<span class="token punctuation">;</span>

<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">test</span><span class="token punctuation">(</span><span class="token class-name">Map</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">User</span><span class="token punctuation">></span></span> map<span class="token punctuation">,</span> <span class="token class-name">String</span> string<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
<span class="token punctuation">&#125;</span>

<span class="token keyword">public</span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">User</span><span class="token punctuation">,</span> <span class="token class-name">Bean</span><span class="token punctuation">></span></span> <span class="token function">test</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
    <span class="token keyword">return</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
<span class="token punctuation">&#125;</span>

<span class="token comment">/**
 * 测试属性类型
 *
 * @throws NoSuchFieldException
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testFieldType</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">NoSuchFieldException</span> <span class="token punctuation">&#123;</span>
    <span class="token class-name">Field</span> field <span class="token operator">=</span> <span class="token class-name">Client</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">.</span><span class="token function">getDeclaredField</span><span class="token punctuation">(</span><span class="token string">"objectMap"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Type</span> gType <span class="token operator">=</span> field<span class="token punctuation">.</span><span class="token function">getGenericType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">// 打印type与generic type的区别</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>field<span class="token punctuation">.</span><span class="token function">getType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>gType<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"**************"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>gType <span class="token keyword">instanceof</span> <span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token class-name">ParameterizedType</span> pType <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> gType<span class="token punctuation">;</span>
        <span class="token class-name">Type</span><span class="token punctuation">[</span><span class="token punctuation">]</span> types <span class="token operator">=</span> pType<span class="token punctuation">.</span><span class="token function">getActualTypeArguments</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name">Type</span> type <span class="token operator">:</span> types<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>type<span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token comment">/**
 * 测试参数类型
 *
 * @throws NoSuchMethodException
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testParamType</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">NoSuchMethodException</span> <span class="token punctuation">&#123;</span>
    <span class="token class-name">Method</span> testMethod <span class="token operator">=</span> <span class="token class-name">Client</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">.</span><span class="token function">getMethod</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token class-name">Map</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">,</span> <span class="token class-name">String</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Type</span><span class="token punctuation">[</span><span class="token punctuation">]</span> parameterTypes <span class="token operator">=</span> testMethod<span class="token punctuation">.</span><span class="token function">getGenericParameterTypes</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name">Type</span> type <span class="token operator">:</span> parameterTypes<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"type -> "</span> <span class="token operator">+</span> type<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>type <span class="token keyword">instanceof</span> <span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
            <span class="token class-name">Type</span><span class="token punctuation">[</span><span class="token punctuation">]</span> actualTypes <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> type<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getActualTypeArguments</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name">Type</span> actualType <span class="token operator">:</span> actualTypes<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
                <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"\tactual type -> "</span> <span class="token operator">+</span> actualType<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">&#125;</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

<span class="token comment">/**
 * 测试返回值类型
 *
 * @throws NoSuchMethodException
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">testReturnType</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">NoSuchMethodException</span> <span class="token punctuation">&#123;</span>
    <span class="token class-name">Method</span> testMethod <span class="token operator">=</span> <span class="token class-name">Client</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">.</span><span class="token function">getMethod</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">Type</span> returnType <span class="token operator">=</span> testMethod<span class="token punctuation">.</span><span class="token function">getGenericReturnType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"return type -> "</span> <span class="token operator">+</span> returnType<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token keyword">if</span> <span class="token punctuation">(</span>returnType <span class="token keyword">instanceof</span> <span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
        <span class="token class-name">Type</span><span class="token punctuation">[</span><span class="token punctuation">]</span> actualTypes <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token class-name">ParameterizedType</span><span class="token punctuation">)</span> returnType<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getActualTypeArguments</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name">Type</span> actualType <span class="token operator">:</span> actualTypes<span class="token punctuation">)</span> <span class="token punctuation">&#123;</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"\tactual type -> "</span> <span class="token operator">+</span> actualType<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">&#125;</span>
    <span class="token punctuation">&#125;</span>
<span class="token punctuation">&#125;</span>

}