Object.clone实现的是浅拷贝，调用clone之后，jvm会检查你是否是继承了Cloneable接口，没有的话直接报错了，有的话申请一块和你的对象一抹一样的大小的内存，然后浅拷贝。

JVM_ENTRY(jobject, JVM_Clone(JNIEnv* env, jobject handle))
JVMWrapper("JVM_Clone");
Handle obj(THREAD, JNIHandles::resolve_non_null(handle));
const KlassHandle klass (THREAD, obj->klass());
JvmtiVMObjectAllocEventCollector oam;if (!klass->is_cloneable()) {
ResourceMark rm(THREAD);
//errorerror
}// Make shallow object copy
const int size = obj->size();
oop new_obj_oop = NULL;
if (obj->is_array()) {
const int length = ((arrayOop)obj())->length();
new_obj_oop = CollectedHeap::array_allocate(klass, size, length, CHECK_NULL);
} else {
new_obj_oop = CollectedHeap::obj_allocate(klass, size, CHECK_NULL);
}Copy::conjoint_jlongs_atomic((jlong*)obj(), (jlong*)new_obj_oop,(size_t)align_object_size(size) / HeapWordsPerLong);
// Clear the header
new_obj_oop->init_mark();BarrierSet* bs = Universe::heap()->barrier_set();
bs->write_region(MemRegion((HeapWord*)new_obj_oop, size));Handle new_obj(THREAD, new_obj_oop);
if (java_lang_invoke_MemberName::is_instance(new_obj()) && java_lang_invoke_MemberName::is_method(new_obj())) {
Method* method = (Method*)java_lang_invoke_MemberName::vmtarget(new_obj());
if (method != NULL) {
methodHandle m(THREAD, method);
m->method_holder()->add_member_name(new_obj());
}
}
if (klass->has_finalizer()) {
new_obj_oop = InstanceKlass::register_finalizer(instanceOop(new_obj()), CHECK_NULL);
new_obj = Handle(THREAD, new_obj_oop);
}
return JNIHandles::make_local(env, new_obj());
}
}