java - Java中的继承是如何实现的？

Question

Java 中继承到底是如何实现的？例如，考虑一下:

class A {
    public void foo() {
         System.out.print("A");
    }
}
class B extends A {
    ...
}
class Test {
    public static void main(String[] args) {
        B test = new B();
        test.foo(); // how is foo() called?
}

在该行下面，编译器是否会将 A.foo() 的定义转储到类 B 的主体中？喜欢

class B extends A {
    ...
    public void foo() {
         System.out.print("A");
    }
}

或者 foo 是否以某种方式在 A 类中查找并在那里调用？

Answer 1

这可能会对您有所帮助，《Ivor Horton's Beginning Java 7》一书中的解释

I said at the beginning of this chapter that a derived class extends a base class. This is not just jargon — it really does do this. As I have said several times, inheritance is about what members of the base class are accessible in a derived class, not what members of the base class exist in a derived class object. An object of a subclass contains all the members of the original base class, plus any new members that you have defi ned in the derived class. This is illustrated in Figure 6-3.