JShell & ki
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際際滷s for a short "mini talk" on using JShell, with a tiny bit on ki (Kotlin interactive shell). JShell and ki are REPLs for Java and Kotlin.
![Accessing other code...
$ ki
ki-shell 0.5.2/1.7.0
type :h for help
[0] :dependsOn org.kiwiproject:kiwi:2.4.0
[1] import org.kiwiproject.collect.KiwiMaps
[2] val m : MutableMap<String, Int> = KiwiMaps.newHashMap("a", 1, "b", 2, "c", 3)
[3] m.put("d", 4)
res3: Int = null
[4] m
res4: MutableMap<String, Int> = {a=1, b=2, c=3, d=4}
Use :dependsOn with artifact coordinates:
groupId:artifactId:version
Yay!Transitive dependencies work!](https://image.slidesharecdn.com/jshell-ki-mini-talk-230123015900-7b07bc2a/85/JShell-ki-17-320.jpg)
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JShell & ki
- 2. Jshell & ki interactive command-line tools REPL (read-evaluate-print-loop) useful for learning & experimenting
- 3. JShell write Java code interactively introduced in JDK 9 create "snippets" of code
- 4. $ jshell | Welcome to JShell -- Version 19 | For an introduction type: /help intro jshell> You type here :-)
- 5. Basics... jshell> import java.time.* jshell> var now = Instant.now() now ==> 2023-01-12T02:47:48.336715Z jshell> now.plusSeconds(15 * 60) $6 ==> 2023-01-12T03:02:48.336715Z jshell> var later = $6 later ==> 2023-01-12T03:02:48.336715Z scratch variable
- 6. Tab completion <press tab again to see documentation> jshell> ZonedDateTime. class from( now( of( ofInstant( ofLocal( ofStrict( parse( jshell> ZonedDateTime.ofInstant( $6 later now Signatures: ZonedDateTime ZonedDateTime.ofInstant(Instant instant, ZoneId zone) ZonedDateTime ZonedDateTime.ofInstant(LocalDateTime localDateTime, ZoneOffset offset, ZoneId zone) <press tab again to see documentation> jshell> ZonedDateTime.ofInstant( just keep pressing tab!
- 7. Show imports jshell> /imports | import java.io.* | import java.math.* | import java.net.* | import java.nio.file.* | import java.util.* | import java.util.concurrent.* | import java.util.function.* | import java.util.prefs.* | import java.util.regex.* | import java.util.stream.* | import org.kiwiproject.collect.* | import com.google.common.collect.* | import java.time.*
- 8. List snippets jshell> /list 1 : import org.kiwiproject.collect.*; 2 : import com.google.common.collect.*; 3 : var m = KiwiMaps.<String, Object>newLinkedHashMap("a", 1, "b", 2, "c", 3); 4 : import java.time.*; 5 : var now = Instant.now(); 6 : now.plusSeconds(15 * 60) 7 : var later = $6;
- 9. Rerun snippets jshell> /list 1 : import org.kiwiproject.collect.*; 2 : import com.google.common.collect.*; 3 : var m = KiwiMaps.<String, Object>newLinkedHashMap("a", 1, "b", 2, "c", 3); 4 : import java.time.*; 5 : var now = Instant.now(); 6 : now.plusSeconds(15 * 60) 7 : var later = $6; jshell> /5 var now = Instant.now(); now ==> 2023-01-12T02:59:43.273136Z jshell> /list 5 5 : var now = Instant.now(); jshell> now now ==> 2023-01-12T02:59:43.273136Z rerun snippet "5"
- 10. Many useful commands work with snippets (list, edit, drop, re-run, save to file, etc.) open file as input source list vars, methods, types, imports set environment (e.g. class & module path, configuration)
- 11. Accessing other code... by default can access only JDK classes use /env to set class and/or module path
- 12. Accessing other code... jshell> /env -class-path .m2/repository/org/kiwiproject/kiwi/2.4.0/ kiwi-2.4.0.jar:.m2/repository/com/google/guava/guava/31.1-jre/guava-31.1- jre.jar:.m2/repository/org/apache/commons/commons-lang3/3.12.0/commons- lang3-3.12.0.jar | Setting new options and restoring state. jshell> import org.kiwiproject.collect.* jshell> var m = KiwiMaps.<String, Object>newLinkedHashMap("a", 1, "b", 2, "c", 3) m ==> {a=1, b=2, c=3} set class (or module) path Beware: you must supply all transitive dependencies! uses Guava's Preconditions
- 13. Use verbose feedback jshell> /set feedback verbose jshell> ZonedDateTime.ofInstant(now, ZoneOffset.UTC) $12 ==> 2023-01-12T02:59:43.273136Z | created scratch variable $12 : ZonedDateTime jshell> /set feedback normal $ jshell -v $ jshell --feedback verbose start in verbose feedback mode ...or change within jshell other feedback modes: concise, normal, silent
- 15. /help is really good in jshell you can learn a ton using it be sure to use its tab completion
- 16. ki Kotlin interactive shell experiment with Kotlin or Java much better than the default REPL (i.e. kotlinc-jvm)
- 17. Accessing other code... $ ki ki-shell 0.5.2/1.7.0 type :h for help [0] :dependsOn org.kiwiproject:kiwi:2.4.0 [1] import org.kiwiproject.collect.KiwiMaps [2] val m : MutableMap<String, Int> = KiwiMaps.newHashMap("a", 1, "b", 2, "c", 3) [3] m.put("d", 4) res3: Int = null [4] m res4: MutableMap<String, Int> = {a=1, b=2, c=3, d=4} Use :dependsOn with artifact coordinates: groupId:artifactId:version Yay!Transitive dependencies work!
- 18. :help Just remember... (alas, ki help is not as helpful as jshell's)
- 19. now get exploring and remember /help (or :help in ki)
- 21. (the end)