[[Category:APIDesignPatterns]]

[[Category:APIDesignPatterns]]

[[Category:APIDesignPatterns:Evolution]]

[[Category:APIDesignPatterns:Evolution]]

</source>

</source>

No problem happened back then. No clash happened. How come? Was it just a pure luck?

No problem happened back then. No clash appeared. How come? Was it just a pure luck?

No! It wasn't a luck. The '''JDK8''' addition of '''chars()''' and '''codePoints()''' was [[BinaryCompatible]]! Because adding new methods into an existing type cannot create a clash, if ''one of the arguments, or the return type is a newly introduced type''!

No! It wasn't a luck. The '''JDK8''' addition of '''chars()''' and '''codePoints()''' was [[BinaryCompatible]]! Because adding new methods into an existing type cannot create a clash, if ''one of the arguments, or the return type is a newly introduced type''!

</source>

</source>

Such fix has to be made across all affected places. Then all applications using affected libraries need to update to their latest versions. Only then such applications can run on '''JDK15'''. That no longer sounds as ''simple'', right? Clearly [[DefaultMethods]] aren't a heaven sent solution, they have some cost! If you are starting to write a new [[API]] and you want to avoid your customers paying that cost, then [[APIvsSPI|separate API from SPI]] and don't mix the [[APIvsSPI|two concepts]] (especially in types that are frequently subclassed/implemented by users of your [[API]]).

Such fix has to be made across all affected places. Then all applications using affected libraries need to update to their latest versions. Only then such applications can run on '''JDK15'''. While the fix is ''simple'', the organizational effort no longer sounds as ''simple'', right? Clearly [[DefaultMethods]] aren't a heaven sent solution, they have some cost! If you are starting to write a new [[API]] and you want to avoid your customers paying that cost, then [[APIvsSPI|separate API from SPI]] and don't mix the [[APIvsSPI|two concepts]] (especially in types that are frequently subclassed/implemented by users of your [[API]]).

=== Why now? Why not then? ===

=== Why now? Why not then? ===

=== Dispatch Directly ===

=== Dispatch Directly ===

It is unfortunate that a code that used to run on older [[JDK]]s, doesn't even link and results in a linkage error on '''JDK15'''. The fix is however ''simple'' - just override the method and dispatch manually:

It is unfortunate that a code that used to run on older [[JDK]]s, doesn't run and leads to a linkage error on '''JDK15'''. The fix is however ''simple'' - just override the method and dispatch manually:

<source lang="java">

<source lang="java">

record Status(boolean empty, boolean large, boolean asciiOnly);

record Status(boolean empty, boolean large, boolean asciiOnly);

default Status status() {

default Status is() {

return Status(length() == 0, length() > 255, codePoints().allMatch((ch) -> ch <= 127);

return Status(length() == 0, length() > 255, codePoints().allMatch((ch) -> ch <= 127);

}

}

</source>

</source>

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.is().empty()'' instead of simpler ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% compatible or the lack of it.

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.is().empty()'' instead of simpler ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% [[BinaryCompatible]] or the lack of it.

=== Future Benefits ===

=== Future Benefits ===

</source>

</source>

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.is().empty()'' instead of simple ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% compatible or the lack of it.

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.is().empty()'' instead of simpler ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% compatible or the lack of it.

=== Future Benefits ===

=== Future Benefits ===

/** @since 15 */

/** @since 15 */

default Status status() {

default Status is() {

return Status(length() == 0);

return Status(length() == 0);

}

}

</source>

</source>

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.status().empty()'' instead of simple ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% compatible or the lack of it.

That'd be completely [[BinaryCompatible]] evolution. People would have to write ''seq.is().empty()'' instead of simple ''seq.isEmpty()''. But does that matter? Not from a [[performance]] perspective - every [[good]] [[JIT]] compiler eliminates any overhead. Then it is just about the will to be 100% compatible or the lack of it.

=== Future Benefits ===

=== Future Benefits ===

[[DefaultMethods]] are useful when one desperately needs to add a method into an existing '''interface'''. There are reasons to [[DefaultMethods#Can_you_disagree.3F|strive to avoid doing that]], however sometimes there is just no way around [[DefaultMethods|doing so]]. That it comeshandy that [[DefaultMethods]] are available since '''JDK8'''. However, use with care. It has recently been demonstrated that adding [[DefaultMethods]] can compromise [[BinaryCompatibility]].

[[DefaultMethods]] are useful when one desperately needs to add a method into an existing '''interface'''. There are reasons to [[DefaultMethods#Can_you_disagree.3F|strive to avoid doing that]], however sometimes there is just no way around [[DefaultMethods|doing so]]. Then it comes handy that [[DefaultMethods]] are available since '''JDK8'''. However, use with care. It has recently been demonstrated that adding [[DefaultMethods]] can compromise [[BinaryCompatibility]].

=== Binary Incompatibility in CharSequence ===

=== Binary Incompatibility in CharSequence ===

[[DefaultMethods]] are useful when one desperately needs to add a method into an existing '''interface'''. There are reasons to [[DefaultMethods#Can_you_disagree.3F|strive to avoid doing that]]), however sometimes there is just no way around [[DefaultMethods|doing so]]. That it comeshandy that [[DefaultMethods]] are available since '''JDK8'''. However, use with care. It has recently been demonstrated that adding [[DefaultMethods]] can compromise [[BinaryCompatibility]].

[[DefaultMethods]] are useful when one desperately needs to add a method into an existing '''interface'''. There are reasons to [[DefaultMethods#Can_you_disagree.3F|strive to avoid doing that]], however sometimes there is just no way around [[DefaultMethods|doing so]]. That it comeshandy that [[DefaultMethods]] are available since '''JDK8'''. However, use with care. It has recently been demonstrated that adding [[DefaultMethods]] can compromise [[BinaryCompatibility]].

=== Binary Incompatibility in CharSequence ===

=== Binary Incompatibility in CharSequence ===