13.4.5

Class Body and Member Declarations

BINARY COMPATIBILITY

Hyper

even though compiling the source for these binaries:

class Hyper { String h = "Hyper"; }

class Super extends Hyper { char h =  h ; }

class Test extends Super {

public static void main(String[] args) {

String s = new Test().h;

System.out.println(s);

}

}

would result in a compile time error, because the

h

 in the source code for

main

would now be construed as referring to the

char

 field declared in

Super

, and a

char

 value can't be assigned to a

String

.

Deleting a class member or constructor that is not declared

private

 may

cause a linkage error if the member or constructor is used by a pre existing binary,

even if the member was an instance method that was overriding a superclass

method. This is because, during resolution, the linker looks only in the class that

was identified at compile time. Thus, if the program:

class Hyper {

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

}

class Super extends Hyper {

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

}

class Test {

public static void main(String[] args) {

new Super().hello();

}

}

is compiled and executed, it produces the output:

hello from Super

Suppose that a new version of class

Super

 is produced:

class Super extends Hyper { }

If

Super

 and

Hyper

 are recompiled but not

Test

, then a

NoSuchMethodError

will result at link time, because the method

hello

 is no longer declared in class

Super

.

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