Define Expressions, Variables and Methods in JShell in Java 9

JShell is a Read-Evaluate-Print Loop (REPL) that evaluates declarations, statements, and expressions as we have entered and immediately shows the results. This tool is run from the command prompt.

In the below, we can define expressions, variables, and methods in JShell.

Expression

We can type any valid Java expression in JShell. The expression is either an arithmetic operation, string manipulation, and method call and evaluates immediately. All the results automatically assigned to a variable created by JShell. These variables have prefixed with $ symbol.

Example

jshell> 10 * 5
$1 ==> 50

jshell> 77 % 3
$2 ==> 2

jshell> $1 + $2
$3 ==> 52

jshell>

Variable

The Variables defined in JShell are the same as defined in a Java program. Once a variable is defined, it is present in the scope.

Example

jshell> String str = "Tutorialspoint"
str ==> "Tutorialspoint"

jshell> str
str ==> "Tutorialspoint"

jshell>

Method

We can define methods in JShell the same as how we can define in Java classes. Once a method has created in a JShell session, we can call it anytime until quitting that session.

Example

jshell> int sum(int x, int y) {
   ...> return x + y;
   ...> }
| created method sum(int,int)

jshell> sum(10,20)
$2 ==> 30

jshell>