Class Base1

base_code/derived_base.cpp:9–16

using namespace std;

class Base1 {
public:
    Base1():value(10) {}
    virtual ~Base1() = default;
    static void test1() { cout << "Base test1..." << endl; }
protected: // 保护
    int value;
};

// 默认为私有继承
class Derived1 : Base1 {