RFR: JDK-8304945: StringBuilder and StringBuffer should implement Appendable explicitly

[Sergey Tsypanov]

On Sat, 1 Apr 2023 17:34:37 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> The StringBuilder and StringBuffer classes are Appendable by virtue of from subclasses their non-public superclass AbstractStringBuilder.
> 
> It is slightly clearer to declare StringBuilder and StringBuffer to directly implement Appendable, as they already directly implement the CharSequence interface also implemented by their superclass.
> 
> There are no other interfaces implemented by AbstractStringBuilder other than Appendable and CharSequence.
> 
> Please also review the CSR https://bugs.openjdk.org/browse/JDK-8305408

src/java.base/share/classes/java/lang/StringBuilder.java line 93:

> 91: public final class StringBuilder
> 92:     extends AbstractStringBuilder
> 93:     implements Appendable, java.io.Serializable, Comparable<StringBuilder>, CharSequence

Not an issue here, just wondering why do we have lots of places where we use `java.io.Serializable` instead of import statement?

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PR Review Comment: https://git.openjdk.org/jdk/pull/13278#discussion_r1155259675