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This commit is contained in:
Marcus Vinicius de Carvalho 2024-10-23 18:30:11 +08:00
parent f5d5e87fa4
commit 0b1fb6c74a
1 changed files with 6 additions and 10 deletions

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@ -3,7 +3,6 @@ public class Main {
// I - Doesn't work because downcast needs to be explicitly declared // I - Doesn't work because downcast needs to be explicitly declared
// ClassC c = new ClassD(); // ClassC c = new ClassD();
// ClassE e = c; // ClassE e = c;
// ClassE e = (ClassE) c;
// II - Can´t upcast because they are from different family branches // II - Can´t upcast because they are from different family branches
// ClassB b = new ClassE(); // ClassB b = new ClassE();
@ -14,21 +13,18 @@ public class Main {
// a.print(12, "there"); // Ok // a.print(12, "there"); // Ok
// a.print(88); // Compilation error // a.print(88); // Compilation error
// IV - We do not have access to a print(String) from the ref C, even though it was downcasted to the obj G // IV -
// ObjectType <- ReferenceType
// Compiler always keep tracking of ObjectType
// While only during Runtime that we will check and execute the ReferenceType
// ClassA a = new ClassC(); // Ok -> Upcast A<-C // ClassA a = new ClassC(); // Ok -> Upcast A<-C
// ClassG g = (ClassG)a; // Ok -> Downcast G<-(A<-C) // ClassG g = (ClassG)a; // Compile Error on some JDKs -> Downcast G<-(A<-C)
// g.print("hello"); // RunTime error: trick // g.print("hello"); // RunTime error
// Upcast is prone to Compiler error // Upcast is prone to Compiler error and Runtime error
// Downcast is prone to Runtime error // Downcast is prone to Runtime error
// V - We lost track of the print(string, string) in C become it become a A first // V - We lost track of the print(string, string) in C become it become a A first
// ClassA a = new ClassC(); // ok // ClassA a = new ClassC(); // ok
// ClassG g = (ClassG)a; // ok // ClassG g = (ClassG)a; // Compile Error on some JDKs
// g.print("hello", "there"); // Runtime error: trick // g.print("hello", "there"); // Runtime error
// VI // VI
// ClassA a = new ClassF(); // OK // ClassA a = new ClassF(); // OK