BINARY COMPATIBILITY

Class Body and Member Declarations

13.4.5

To preserve binary compatibility, methods should not be deleted; instead,

 forwarding methods  should be used. In our example, replacing the declaration

of

Super

 with:

class Super extends Hyper {

void hello() { super.hello(); }

}

then recompiling

Super

 and

Hyper

 and executing these new binaries with the

original binary for

Test

, produces the output:

hello from Hyper

as might have naively been expected from the previous example.

The

super

 keyword can be used to access a method declared in a superclass,

bypassing any methods declared in the current class. The expression:

super.

Identifier

is resolved, at compile time, to a method

M

 declared in a particular superclass

S

.

The method

M

 must still be declared in that class at run time or a linkage error will

result. If the method

M

 is an instance method, then the method

MR

 invoked at run

time is the method with the same signature as

M

 that is a member of the direct

superclass of the class containing the expression involving

super

. Thus, if the

program:

class Hyper {

void hello() { System.out.println("hello from Hyper"); }

}

class Super extends Hyper { }

class Test extends Super {

public static void main(String[] args) {

new Test().hello();

}

void hello() {

super.hello();

}

}

is compiled and executed, it produces the output:

hello from Hyper

Suppose that a new version of class

Super

 is produced:

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