1.首先類如下：

package test;

public class Outer {

    private Outer() {

    }

    private void eat(String food) {
        System.out.println("我在吃"+food);
    }

    class Inner{

        private Inner(){

        }
        private void go(String city){
            System.out.println("我要去"+city);
        }
    }

}
 

2.呼叫方法的類

package test;

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

public class MainTest {

    public static void main(String[] args) {

        try {
            Class clz = Class.forName("test.Outer");
            System.out
 
.println(clz);

            Class clz1 = Class.forName("test.Outer$Inner");
            System.out.println(clz1);

            // 獲取外部類方法
            Method mt = clz.getDeclaredMethod("eat", String.class);
            System.out.println(mt);

            // 獲取內部類的方法
            Method mt1 = clz1.getDeclaredMethod
 
("go", String.class);
            System.out.println(mt1);

            // 獲取外部類的構造器
            Constructor c = clz.getDeclaredConstructor();
            System.out.println(c);
            c.setAccessible(true);// 使得外部私有構造器可以被訪問

            // 獲取內部構造器
            Constructor c1 = clz1.getDeclaredConstructors()[0];
            c1.setAccessible(true);
            System.out.println(c1);

            // 呼叫外部類的方法eat()
            mt.setAccessible(true);// 給私有方法賦許可權，使其可以被操作
            mt.invoke(c.newInstance(), "米飯");

            // 呼叫內部類的方法
            mt1.setAccessible(true);// 理由同上
            mt1.invoke(c1.newInstance(c.newInstance()), "蘇州");

        } catch (ClassNotFoundException 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();
        } 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 (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

3.輸出結果

class test.Outer
class test.Outer$Inner
private void test.Outer.eat(java.lang.String)

private void test.Outer$Inner.go(java.lang.String)
private test.Outer()

private test.Outer$Inner(test.Outer)
我在吃米飯
我要去蘇州