Read-Eval-Print-Loop is the full form of REPL. With JShell, java has REPL capability. By using REPL, we can easily code and test Java-based logic without assembling using javac and you can see the result of calculations directly.
Open a command prompt and write jshell
$ jshell ' Welcome to JShell -- Version 9-ea ' For an introduction type: /help intro jshell>
Write/help one time when jshell commands start running.
jshell> /help ' Type a Java language expression, statement, or declaration. ' Or type one of the following commands: ' /list [<name or id>'-all'-start] ' list the source you have typed ' /edit <name or id> ' edit a source entry referenced by name or id ' /drop <name or id> ' delete a source entry referenced by name or id ' /save [-all'-history'-start] <file> ' Save snippet source to a file. ' /open <file> ' open a file as source input ' /vars [<name or id>'-all'-start] ' list the declared variables and their values ' /methods [<name or id>'-all'-start] ' list the declared methods and their signatures ' /types [<name or id>'-all'-start] ' list the declared types ' /imports ' list the imported items
Write /import one time when jshell commands start running and view the used 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.* jshell>
Try running easy calculations in JShell.
jshell> 3+1 $1 ==> 4 jshell> 13%7 $2 ==> 6 jshell> $2 $2 ==> 6 jshell>
Generate a function doubled() to take an int and return its doubled value.
jshell> int doubled(int i){ return i*2;} ' created method doubled(int) jshell> doubled(6) $3 ==> 12 jshell>
Write/exit.
jshell> /exit ' Goodbye