Write a method to decide whether a string contains a valid IPv$6$ address in the preferred

format $($each $h$ represents a hexadecimal digit$)$:

hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh

your method must loop through individual characters in the string.

Approaches using regular expression and$/$or API classes like Pattern, Matcher will

receive zero credit.

Your program $($i$.$e$.$ your class$)$ will have two methods, the actual method and a main$(.$

Start with a method stub like the one below. The main$(0$ will be used to test your method

with different data $($see ch$6\mathrm{.}7$ Unit testing$).$

Here are examples of valid and invalid IPv$6$ addresses:

Valid:

$0123$:$4567$:$89$ab:cdef:$0123$:$4567$:$89$Ab:cDEf

$0000$:$0000$:$0000$:dddd:eee:dddd:eeee:ffff

$0000$:$0000$:$0000$:$0000$:$0000$:$0000$:$0000$:$0000$

Invalid:

$123$:$4567$:$89$ab:cdef:$0123$:$4567$:$89$ab:cdef$0->$ not $4$ hex digits in $1^{st}$ and last

groups

$0000$:$0000$:$0000$ not enough digits$/$groups

$01$hg:$4567$:$89$ab:cdef:$0123$:$4567$:$89$ab:cdef $$ non$-$hex digits in the $1^{st}$ group

$0123$:$4567$::$89$b:cdef:$0123$:$4567$:$89$ab:cdef $->$ two colons together

Use a proper incremental development strategy to build your program. It is a good idea to

first check whether the parameter string is of the right length.

Follow the unit testing examples to add at least $3$ more testing cases of your choice to

your main$()$: $1$ valid address and $2$ invalid ones.

When you are done, include a screenshot of the execution of your program in your

assignment report document. If it works properly, your program should only print those

two lines:

Testing started $...$

Testing completed.