JShell: representation of array values

[Ben Evans]

Hi Robert,

Some feedback from my wife, who's currently writing some introductory
material for absolute beginners in Java (& programming as a whole) -
she uses jshell as the very first thing that learners meet and had
this to say:

> seeing a visual representation of the array like that would be a great help!

> (Right now you have to use iterations to see what's in the array, and that's brining in logic far earlier than I'd like)

> I really liked in earlier versions where it returned a type as well as a result - helps learners get to grips with java as typed language.

> (Also makes it easier for kids who are used to calculators to understand why 4/3 returns 1, not 1.333334!)

If the usage of jshell for beginners is a big aim of the project
(something like Swift Playgrounds), Anna & I would be happy to help
review features & provide more feedback with that audience in mind.

Thanks,

Ben


On Thu, Sep 22, 2016 at 6:46 AM, Robert Field <robert.field at oracle.com> wrote:
> JavaOne demos made it clear we need a friendlier representation of array
> values.
>
> Current --
>
> jshell> new String[] { "hi", "low", null }
> $2 ==> [Ljava.lang.String;@ae45eb6
>
> jshell> new char[] { 'a', 34, 77 }
> $3 ==> [C at 27efef64
>
> I'm proposing this --
>
> jshell> new int[4]
> $1 ==> int[4] { 0, 0, 0, 0 }
>
> jshell> new int[0]
> $2 ==> int[0] {  }
>
> jshell> new String[] { "hi", "low", null }
> $3 ==> String[3] { "hi", "low", null }
>
> jshell> new char[] { 'a', 34, 77 }
> $4 ==> char[3] { 'a', '"', 'M' }
>
> jshell> new int[][] { new int[] {44, 55}, new int[] {88,99}}
> $5 ==> int[][2] { int[2] { 44, 55 }, int[2] { 88, 99 } }
>
> jshell> new Object[] { "howdy", new int[] { 33, 44, 55 }, new String[] {
> "up", "down" }}
> $6 ==> Object[3] { "howdy", int[3] { 33, 44, 55 }, String[2] { "up", "down"
> } }
>
> jshell> new int[100000]
> $7 ==> int[100000] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ...
>
> jshell>
>
>
> Comments???
>
> Thanks,
> Robert
>