Conversions between parent and child classes

Conclusion:

1. Parent class (Basic Class) Rotor class (extension Class), error

2. Subclass (Extension Class) to parent class (base class), successful

The experiment is as follows:

Parent class (base class)

 Public classPerson {PrivateString name; PrivateString Doc;  PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     PublicString Getdoc () {returnDoc; }     Public voidSetdoc (String doc) { This. doc =Doc; }}

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Subclass (Extension Class)

 Public class extends Person {}

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Implementation class:

@Test//failed     Public voidtest1 () {person P=NewPerson (); P.setname ("Name"); Cnperson CP=(Cnperson) p;    System.out.println (Cp.getname ()); } @Test//Success     Public voidtest2 () {Cnperson CP=NewCnperson (); Cp.setname ("Name"); Person P=(person) CP;    System.out.println (P.getname ()); }

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Conversions between parent and child classes