java，reflection，innerclass， [英] java, reflection , innerclass,

问题描述

您好我想使用反射获取内部类的对象，但我收到了一些错误。

Hi i want to get the object of inner class using reflection but i am getting some error in it.

代码是： -

package reflaction;
public class MyReflection {
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException  {
    Class obj = Class.forName("reflaction.MyReflection$TestReflection");
    TestReflection a = (TestReflection) obj.newInstance();
    a.demo();
}

class TestReflection {

    public void demo(){
        System.out.println("reflection occurs");
    }
    }
}

，错误是： - -

and the error is :--

Exception in thread "main" java.lang.InstantiationException: reflaction.MyReflection$TestReflection
    at java.lang.Class.newInstance0(Class.java:357)
    at java.lang.Class.newInstance(Class.java:325)
    at reflaction.MyReflection.main(MyReflection.java:10)

推荐答案

使用此：

public class MyReflection {

public static void main(String[] args) throws ClassNotFoundException,
        InstantiationException, IllegalAccessException,
        NoSuchMethodException, SecurityException, IllegalArgumentException,
        InvocationTargetException {
    Class outer = Class.forName("reflaction.MyReflection");
    Object outerInstance = outer.newInstance();

    Class<?> inner = Class
            .forName("reflaction.MyReflection$TestReflection");
    Constructor<?> constructor = inner.getDeclaredConstructor(outer);

    TestReflection innerInstance = (TestReflection) constructor
            .newInstance(outerInstance);

    innerInstance.demo();
}

class TestReflection {

    public void demo() {
        System.out.println("reflection occurs");
    }
}

看一下 Javadoc getDeclaredConstructor（Class<？> ... parameterTypes）。它说：

...如果此Class对象表示在非静态上下文中声明的内部类，则形式参数类型包括显式封闭实例作为第一个参数。

... If this Class object represents an inner class declared in a non-static context, the formal parameter types include the explicit enclosing instance as the first parameter.

因此，将封闭实例作为第一个参数将创建内部类的新实例：

So, giving the enclosing instance as first parameter will create a new instance of the inner class:

    TestReflection innerInstance = (TestReflection) constructor
            .newInstance(outerInstance);

这篇关于java，reflection，innerclass，的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！