How to implement an ArrayList using JShell in Java 9?

JavaObject Oriented ProgrammingProgramming

JShell is an interactive Java Shell tool that enables us to execute java code from the shell and instantly displays the output. JShell is the REPL(Read Evaluate Print Loop) tool that runs from the command-line. We can start a JShell by simply typing "jshell" in the command prompt, and to exit the jshell by using "/exit" command. For small snippets, we do not need to create a main() method in JShell.

We can also implement the major collections like list, map and set by using this tool. In the below program, we can implement an ArrayList with various scenarios.


C:\Users\User\Desktop\Java 9 QNA>jshell
| Welcome to JShell -- Version 9.0.4
| For an introduction type: /help intro

jshell> ArrayList<String> list = new ArrayList<String>();
list ==> []

jshell> list.add("Jai");list.add("Adithya");list.add("Raja");list.add("Chaitanya");
$2 ==> true
$3 ==> true
$4 ==> true
$5 ==> true

jshell> list
list ==> [Jai, Adithya, Raja, Chaitanya]

jshell> list.isEmpty()
$7 ==> false

jshell> list.get(3)
$8 ==> "Chaitanya"

jshell> list.get(9)
|    java.lang.IndexOutOfBoundsException thrown: Index 9 out-of-bounds for length 4
|       at Preconditions.outOfBounds (
|       at Preconditions.outOfBoundsCheckIndex (
|       at Preconditions.checkIndex (
|       at Objects.checkIndex (
|       at ArrayList.get (
|       at (#9:1)

jshell> list.size()
$10 ==> 4

jshell> if(list.isEmpty()) System.out.println("Empty"); else System.out.println("Not Empty");
Not Empty
Updated on 11-Mar-2020 13:52:23