Java inherits internal class issues (Java programming thought notes)

The normal inner class holds a reference to the owning external class by default. If a new class is defined to inherit the inner class, how is the "secret" reference initialized?

Java provides a special syntax:

1 classEGG2 {2      Public classyolk{3          Publicyolk () {4System.out.println ("Egg2.yolk");5         }6     }7 }8 classBIGEGG2 {9      Public classYolkextendsEgg2.yolk {Ten          Publicyolk () { One         } A     } -}

Above this code compilation cannot pass, the error is in 10 lines, the error is:

No enclosing instance of type EGG2 is available due to some
Intermediate constructor invocation

Modify the code to:

1 classEGG2 {2      Public classyolk{3          Publicyolk () {4System.out.println ("Egg2.yolk");5         }6     }7 }8 classBIGEGG2 {9      Public classYolkextendsEgg2.yolk {Ten          PublicYolk (Egg2 egg2) { OneEgg2.Super() ; A         } -     } -}

Egg2.super () was added in line 11, so the compilation passed the ~~

Then look at another piece of code that seems to contradict the above conclusion:

1 classEGG2 {2      Public classyolk{3          Publicyolk () {4System.out.println ("Egg2.yolk");5         }6     }7 }8 classBigEgg2extendsEGG2 {9      Public classYolkextendsEgg2.yolk {Ten          Publicyolk () { One         } A     } -}

Note that 8 rows of inheritance and 11 rows do not use the Super statement, but this code compiles properly, why?

I guess the reason:

The super syntax is used to get the derived class to obtain a reference to the perimeter class, that is, to get the Bigegg2.yolk Class A reference to EGG2. Looking at the code above, BigEgg2 inherits from Egg2, so BIGEGG2 has a reference to EGG2.

Bigegg2.yolk is the inner class of BigEgg2, so yolk implicitly holds a reference to BIGEGG2, so through this reference chain, Bigegg2.yolk has a reference to EGG2. So you don't need to use super syntax.

Java inherits internal class issues (Java programming thought notes)