java - 由java中的所有类扩展的默认类

Question

Java中有没有默认所有类都扩展的Default Class？

示例:如果我有一个像这样的简单类:

Class A {
  String a;
}

这个类是不是默认继承了一个类？

Answer 1

java.lang.Object类是所有类的父类(super class)。

Class Object is the root of the class hierarchy. Every class has Object as a superclass. All objects, including arrays, implement the methods of this class.

你可以测试一下:

A a = new A();
if(a instanceof Object){
  System.out.println("Object is superclass of all classes");
}