如何保护类,使它们在包外不可见

把所有的关键词都删掉。默认可见性为 package-private ,仅在包中可见。

例如。:

// class Foo is public
public class Foo
{
    final private Bar bar = ...;
}

// class Bar is package-private
// (visible to all classes in the package, not visible outside the package)
class Bar
{
    ...;
}