jni如何复写方法

Question

package com.xx.test;
class Test {
  public static void make(String a, Object obj); 

  //obj = new testa() {
     public void method2() {}
   }
}

package com.xx.testa;
class testa {
    public void method2() {
    //todo
    }
}

JNIEXPORT void JNICALL Java_com_xx_test_make(JNIEnv *env, jclass type,  jstring str, jobject obj) {
//如何在这里初始化并复写testa？

}