使用反射时，您会发现该内部类的构造函数将外部类的实例作为附加参数（总是第一个）。
例：
import java.lang.reflect.Constructor;import java.lang.reflect.InvocationTargetException;public class OuterClass { private class InnerClass { } public OuterClass() { super(); } public static void main(String[] args) { // instantiate outer class OuterClass outer = new OuterClass(); // List all available constructors. // We must use the method getDeclaredConstructors() instead // of getConstructors() to get also private constructors. for (Constructor<?> ctor : OuterClass.InnerClass.class .getDeclaredConstructors()) { System.out.println(ctor); } try { // Try to get the constructor with the expected signature. Constructor<InnerClass> ctor = OuterClass.InnerClass.class .getDeclaredConstructor(OuterClass.class); // This forces the security manager to allow a call ctor.setAccessible(true); // the call try { OuterClass.InnerClass inner = ctor.newInstance(outer); System.out.println(inner); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block e.printStackTrace(); } } catch (NoSuchMethodException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SecurityException e) { // TODO Auto-generated catch block e.printStackTrace(); } }}
