How does Java reflection mechanism deal with inner classes?

The Java reflection mechanism requires two steps to process internal classes: obtain the class object of the external class, obtain the class object of the internal class, and then create an internal class instance through the external class instance. Members and methods of an inner class can be accessed through reflection, such as getting an inner class method and calling it through an inner class instance.

How the Java reflection mechanism handles inner classes

Introduction

The reflection mechanism allows Java code inspects and modifies objects at runtime. When dealing with inner classes, reflection requires some extra steps.

Processing inner classes

To obtain the class object of the inner class, you must first obtain the class object of its outer class. The following is a Java code example:

Class<?> outerClass = Class.forName("com.example.OuterClass");
Class<?> innerClass = outerClass.getDeclaredClasses()[0];

Instantiating an inner class

To instantiate an inner class, you need to use an outer class instance. The following code example shows how to create an inner class instance:

OuterClass outer = new OuterClass();
内部类 inner = (内部类) innerClass.newInstance(outer); //需要将外部类实例作为参数

Accessing inner class members

Reflection also allows access to members of inner classes. The following code example shows how to access internal class methods:

Method innerMethod = innerClass.getDeclaredMethod("innerMethod");
innerMethod.invoke(inner);

Practical case

The following is a Java reflection practical case for processing inner classes:

import java.lang.reflect.Class;
import java.lang.reflect.Method;

public class InnerClassDemo {
    public static void main(String[] args) throws Exception {
        // 获取外部类类对象
        Class<?> outerClass = Class.forName("com.example.OuterClass");

        // 获取内部类类对象
        Class<?> innerClass = outerClass.getDeclaredClasses()[0];

        // 访问内部类成员
        Method innerMethod = innerClass.getDeclaredMethod("innerMethod");

        // 创建外部类实例
        OuterClass outer = new OuterClass();

        // 创建内部类实例
        内部类 inner = (内部类) innerClass.newInstance(outer);

        // 调用内部类方法
        innerMethod.invoke(inner);
    }
}

In this example, we use reflection to get the class object of the inner class, create an instance of the inner class, and call its methods.

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