How to handle instantiated C++ object from JAVA through JNI(NDK)

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := SampleCode
LOCAL_SRC_FILES := package_name_ToasterSample.cpp

include $(BUILD_SHARED_LIBRARY)

jniConfig.sh

# check Signatures
javap -classpath bin/classes -p -s com.example.helloJni

#auto-generate header files
javah -classpath bin/classes com.example.hellojni.HelloJni

package_name_ToasterSample.cpp

#include "package_name_ToasterSample.hh"

using namespace MyNamespace::SampleCode;

Sampler::Sampler()
: _value(0), _str(nullptr), _ptr(0)
{
	_ptr = reinterpret_cast<jlong>(this);
}

Sampler::Sampler(jlong ptr)
: _value(0), _str(nullptr), _ptr(ptr)
{
}

Sampler::~Sampler()
{
}

Sampler* Sampler::GetSampler(jlong ptr)
{
	Sampler *s = reinterpret_cast<Sampler *>(ptr);
	return s;
}

int Sampler::GetValue()
{
	return this->_value;
}

void Sampler::SetValue(int v)
{
	this->_value = v;
}


JNIEXPORT jlong JNICALL Java_me_moda_deleteme_ToasterSample_createToaster (JNIEnv *, jobject)
{
	Sampler *sampler = new Sampler();
	return reinterpret_cast<jlong>(sampler);
}

JNIEXPORT void JNICALL Java_me_moda_deleteme_ToasterSample_deleteToaster
(JNIEnv *, jobject, jlong ptr)
{
	Sampler *sampler = Sampler::GetSampler(ptr);
	delete sampler;
}

JNIEXPORT jint JNICALL Java_me_moda_deleteme_ToasterSample_getValue(JNIEnv *env, jobject obj, jlong ptr)
{
	Sampler *s = Sampler::GetSampler(ptr);
	return (int)(s->GetValue());
}

JNIEXPORT void JNICALL Java_me_moda_deleteme_ToasterSample_setValue(JNIEnv *env, jobject obj, jlong ptr, jint value)
{
	Sampler *s = Sampler::GetSampler(ptr);
	s->SetValue(value);
}

ToasterSample.java

package package.name.deleteme;

public class ToasterSample 
{
	static {
		System.loadLibrary("SampleCode");
	}
	
	public static ToasterSample getToaster() { 
		return new ToasterSample();
	}
	
	public ToasterSample() {
		super();	
		_ptr = createToaster();
	}
	
	protected void finalize() { deleteToaster(); }
	private synchronized void deleteToaster() { deleteToaster(_ptr); }
	
	private long _ptr;
	
	private int _value;
	private static String _str;
	
	private native long createToaster();
	private native void deleteToaster(long ptr);
	
	public int getValue() {
		return getValue(_ptr);
	}
	public void setValue(int v) {
		setValue(_ptr, v);
	}
	private native int getValue(long ptr);
	private native void setValue(long ptr, int v);
	
	public static native String getStr();
	public static native void setStr(String str);
}