CLASSES

Inheritance, Overriding, and Hiding

8.4.6

class DizzyDean {

int pitch() { throw new RuntimeException("90 mph?!"); }

}

8.4.6   Inheritance, Overriding, and Hiding

A class

inherits

 from its direct superclass and direct superinterfaces all the meth 

ods (whether

abstract

 or not) of the superclass and superinterfaces that are

accessible to code in the class and are neither overridden ( 8.4.6.1) nor hidden

( 8.4.6.2) by a declaration in the class.

8.4.6.1

Overriding (By Instance Methods)

If a class declares an instance method, then the declaration of that method is said

to

override

 any and all methods with the same signature in the superclasses and

superinterfaces of the class that would otherwise be accessible to code in the class.

Moreover, if the method declared in the class is not

abstract

, then the declara 

tion of that method is said to

implement

 any and all declarations of

abstract

methods with the same signature in the superclasses and superinterfaces of the

class that would otherwise be accessible to code in the class.

A compile time error occurs if an instance method overrides a

static

method. In this respect, overriding of methods differs from hiding of fields ( 8.3),

for it is permissible for an instance variable to hide a

static

 variable.

An overridden method can be accessed by using a method invocation expres 

sion ( 15.11) that contains the keyword

super

. Note that a qualified name or a

cast to a superclass type is not effective in attempting to access an overridden

method; in this respect, overriding of methods differs from hiding of fields. See

 15.11.4.10 for discussion and examples of this point.

8.4.6.2

Hiding (By Class Methods)

If a class declares a

static

 method, then the declaration of that method is said to

hide

 any and all methods with the same signature in the superclasses and super 

interfaces of the class that would otherwise be accessible to code in the class. A

compile time error occurs if a

static

 method hides an instance method. In this

respect, hiding of methods differs from hiding of fields ( 8.3), for it is permissible

for a

static

 variable to hide an instance variable.

A hidden method can be accessed by using a qualified name or by using a

method invocation expression ( 15.11) that contains the keyword

super

 or a cast

to a superclass type. In this respect, hiding of methods is similar to hiding of

fields.

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