Two dimensional Arrays

**masterT** · July 18th, 2011, 06:14 PM

I've posted this on another part of this forum as well but more people are viewing in here.

I know most about them but the one thing I can't work out is, how do you put one Arrays values into another?

Something about nested for loops? Not sure how to do them though...?

I basically need to do this:

Write a public instance method called writeLetter() which takes a single argument
of type char called aCharacter and returns no result. The method should first invoke
the getLetter() method on the LEDFont class with aCharacter as its argument. As
stated earlier, getLetter() returns a two-dimensional array of type boolean which
has has CONSTANT_ONE rows and CONSTANT_TWO columns,
representing the LED settings for aCharacter. The array should be assigned to an
appropriately declared local variable called letter. The method should then copy the
boolean values from letter into matrix starting at the first row and column,
overwriting existing values.

>>>Little back ground about this,

LEDFont is purely just used for its "getLetter" method, so I need to invoke that method and it will then return a two dimensional boolean Array.

matrix is a 2D boolean Array which outputs a display, its values make up 5 rows and 60 columns so at this stage them elements are false and are represented by a '.' but if any elements are true then that true element will be represented by a 'O' .

So basically the 2D boolean Array that is returned (letter), its values and elements need to go into 'matrix' so that it can output what ever the user entered for aCharacter.

I hope all this makes sense!

**dlorde** · July 18th, 2011, 06:19 PM

Originally Posted by masterT

I've posted this on another part of this forum as well but more people are viewing in here

I think you'll find that multiple posting is not considered cool.

If you want help with nested loops, just ask.

**masterT** · July 18th, 2011, 06:30 PM

I have removed the

........................................
Should I remove one of the threads as well if its offending you?

**dlorde** · July 18th, 2011, 06:47 PM

Originally Posted by masterT

Should I remove one of the threads as well if its offending you?

It doesn't offend me, it's just thoughtless. The mods will probably remove it.

**masterT** · July 18th, 2011, 07:17 PM

Hi dlorde, please forgive me.... Im going a little crazy and I just need help (famous last words!) I'm kinda in a thoughtless mood to be honest and would appreciate any help that you could give me. I know when you see things like this, you probably just want to move onto the next thread but please help. If a mod can remove the other one then ok then but for now if an expert like you can help then please do

**dlorde** · July 18th, 2011, 07:20 PM

So what are you asking, exactly? The more specific the question, the more specific the answer is likely to be.

If you want help with nested loops, just ask.

**masterT** · July 18th, 2011, 07:25 PM

Ok, so how can I put values from one 2D array into another using a nested loop?

**dlorde** · July 18th, 2011, 07:52 PM

If you think of the array in terms of multiple rows, with multiple items in each row (i.e. rows & columns). You write a loop that iterates over the rows, using a row counter, so it deals with one row (array of items) each time round; then inside that loop, you write another loop that takes the current row and iterates over it using a column counter, to access each column (item) in the row. So for each item, you'll have the row index and the column index, so you can copy that item from the 2D source array to the 2D destination array:

destinationArray[rowIndex][columnIndex] = sourceArray[rowIndex][columnIndex];

Don't forget that array indexes start at zero, and be sure that the destination array has been initialized to the correct size.

**masterT** · July 18th, 2011, 08:28 PM

Hi dlorde, I noticed you commented on an exact same problem thread > http://www.javaprogrammingforums.com...n-array-5.html <
So in this case you also mention about a single loop? How can this be done? Do you have any examples? With the 2D boolean array that is mentioned "letter" we dont actually get the elements value, its just returned by LEDFont so that we can use it to over ride matrix...

Sounds pretty stupid, but hey thats our great assignment!

**Norm** · July 18th, 2011, 08:51 PM

about a single loop? How can this be done?

The single loop copied a full row at each time around the loop.
A two dim array is made up of a bunch of one dim arrays. For example:
<type>[][] twoDim = new <type>[10][5];
Then
twoDim[0] is a one dim array of <type>[5]
the same for the other indexes from 1 to 9. A total of 10 one dim arrays with 5 elements each.

**dlorde** · July 19th, 2011, 05:37 PM

Thanks Norm

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