java - 我如何能够在类中引用实例的私有(private)字段？

Question

我一直在寻找解释，但没能找到。为什么这段代码有效？具体来说——为什么可以访问实例的私有(private)成员？据我所知，只有在原始类中的方法中创建实例时，它才有效。

public class MyClass {
    private int thing;

    public MyClass () {}

    public MyClass makeMe () {
        MyClass myClass = new MyClass();
        myClass.thing = 1;
        return myClass;
    } 
}

Answer 1

私有(private)字段只能由该类访问。您仍在 MyClass 的实例中操作，因此您无需使用 setter 即可看到和访问私有(private)字段。

更正式一点... JLS 6.6.1谈论访问。

这是删节的片段，强调我的:

• A member (class, interface, field, or method) of a reference (class, interface, or array) type or a constructor of a class type is accessible only if the type is accessible and the member or constructor is declared to permit access:

  • ...Otherwise, if the member or constructor is declared private, then access is permitted if and only if it occurs within the body of the top level class (§7.6) that encloses the declaration of the member or constructor.