New switch Expressions in Java 12_java 17(에러메세지 해결) (use --enable-preview to enable patterns in switch statements)

https://blogs.oracle.com/javamagazine/post/new-switch-expressions-in-java-12

 

 

에러 메세지

src/Start.java:8: error: patterns in switch statements are a preview feature and are disabled by default.
            case Sleeping sl -> System.out.println("Wake up!" + sl.hours);
                 ^
  (use --enable-preview to enable patterns in switch statements)

 

 

 

 

 

java --enable-preview Start

Start 는 컴파일 하고 나온 실행 파일

Start.class

 

 

17 뭐시기 에러나서 해결함. 

오라클 들어가서 

 다운로드까지 ㅋㅋ

 

 

https://www.oracle.com/java/technologies/javase/jdk12-archive-downloads.html

 

 

12 로 해도 에러 나서 

javac --enable-preview --release 12 Start.java
error: invalid source release 12 with --enable-preview
  (preview language features are only supported for release 17)

 

 

17로 컴파일 해줌.

javac --enable-preview --release 17 Start.java
Note: Start.java uses preview features of Java SE 17.
Note: Recompile with -Xlint:preview for details.

 

 

ls
Activity.class Coding.class   Skiing.class   Sleeping.class Start.class    Start.java

 

 

java --enable-preview Start
Wake up!9

 

 

성공 !!!

 

❤️