👌 IMPROVE: add comments explaining errors

Signed-off-by: Jonas Sulzer <jonas@violoncello.ch>

src/Ex_05/AbstractFinal.java

@@ -5,12 +5,12 @@ class AbstractFinal {
 
         A[] tab = new A[3];
 
-        tab[0] = new A();
+        tab[0] = new A(); // abstract class can't be initialized
         tab[1] = new B();
         tab[2] = new C();
 
-        tab[1].b = 2;
-        ((C)tab[2]).c = 3;
+        tab[1].b = 2; // tab is of type A, so b can't be accessed as it's not defined in A
+        ((C)tab[2]).c = 3;  // final can't be modified
     }
 }
 
@@ -35,7 +35,7 @@ abstract class D extends A {
 
     abstract int calcul(int b) {
 
-    }
+    } // abstract class can't have content
 
     abstract int machin();
 }
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