Java Reference
In-Depth Information
It is a compile-time error if the ClassType names the class Enum or any invocation of it.
If the TypeDeclSpecifier is followed by any type arguments, it must be a correct invocation
of the type declaration denoted by TypeDeclSpecifier , and none of the type arguments may
be wildcard type arguments, or a compile-time error occurs.
Given a (possibly generic) class declaration for C < F 1 ,..., F n > ( n ≥ 0, C Object ), the direct
superclass of the class type C < F 1 ,..., F n > is the type given in the extends clause of the declar-
ation of C if an extends clause is present, or Object otherwise.
Let C < F 1 ,..., F n > ( n > 0) be a generic class declaration. The direct superclass of the
parameterized class type C < T 1 ,..., T n > , where T i (1 ≤ i n ) is a type, is D < U 1 θ,..., U k
θ > , where D < U 1 ,..., U k > is the direct superclass of C < F 1 ,..., F n > , and θ is the substitution
[ F 1 := T 1 ,..., F n := T n ] .
The direct superclass of an enum type E is Enum< E > .
A class is said to be a direct subclass of its direct superclass. The direct superclass is the
class from whose implementation the implementation of the current class is derived.
Example 8.1.4-1. Direct Superclasses and Subclasses
Click here to view code image
class Point { int x, y; }
final class ColoredPoint extends Point { int color; }
class Colored3DPoint extends ColoredPoint { int z; } // error
Here, the relationships are as follows:
• The class Point is a direct subclass of Object .
• The class Object is the direct superclass of the class Point .
• The class ColoredPoint is a direct subclass of class Point .
• The class Point is the direct superclass of class ColoredPoint .
The declaration of class Colored3dPoint causes a compile-time error because it attempts
to extend the final class ColoredPoint .
The subclass relationship is the transitive closure of the direct subclass relationship. A class
A is a subclass of class C if either of the following is true:
A is the direct subclass of C
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