2

I have a few multidimensional arrays of type char[][]. Eg..

char[][] ARRAY_1 = {
    {'.','#'},
    {'$','@'}
}
char[][] ARRAY_2 = {
    {'.','#'},
    {'$','@'}
}

And I want to make an array or list of some sort such as

ARRAY = {ARRAY_1,ARRAY_2,...}

so I'll be able to put in ARRAY[1] (or something similar) and have it return the entire char[][] ARRAY_1

I am very new to programming with Java so I'm not sure what the best way to do this is.

Edit: I've just found out I'm not allowed to use ArrayLists.

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4
  • Stackoverflow previous question-> stackoverflow.com/questions/8321956/list-of-arrays-in-java Commented May 26, 2018 at 3:30
  • "And I want to make an array or list of some sort ..." - Please be clear about what you want. Arrays and lists are different, and there are many ways to create them so the answer will depend on what you want. Commented May 26, 2018 at 3:40
  • 1
    mm if you are at java 9 List.of(ARRAY_1,ARRAY_2); Commented May 26, 2018 at 3:41
  • @soorapadman 9 or 10, haha! Commented May 26, 2018 at 3:49

4 Answers 4

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4

Direct answer: use ArrayList<char[][]> or char[][][].

Basically, you create an ArrayList that holds your 2 dimensional arrays or a 3 dimensional array of chars.

List<char[][]> array = new ArrayList<>();

or

char[][][] array = char[length][][];

To add the arrays, you just use the following:

array.add(arrayOne); //for an ArrayList
array.add(arrayTwo);

or

array[0] = arrayOne; //for an array
array[1] = arrayTwo;

To get the arrays, you just use the following (where the number is the index):

array.get(0); //for an ArrayList
array.get(1);

or

array[0]; //for an array
array[1];

Check out the ArrayList javadoc for more information.

(edit: variable changed to match naming conventions)

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4 Comments

I thought you can't use primitive types in java generics? Shouldn't it be Character[][] instead of char[][], or am I missing something?
Can you explain the char[][][] method? I've tried using it but I'm having trouble calling the array later on.
@MarDev in Java, arrays are treated as objects, and, therefore, no wrapper class is necessary.
@MarDev char[][] is actually an object which contains a sequence of chars (or in this case a sequence of a sequence of chars, but you get the idea)
1

So ... if you are not allowed to use lists ... this is one way to make an array of existing arrays.

 char[][][] ARRAY = new char[][][]{ARRAY_1, ARRAY_2};

Insight #1: an N-dimension array in Java is an array of N-1 dimension arrays (assuming N > 1).

Insight #2: arrays are indexed from zero.

How would I call the arrays individually again later on?

  1. You still have the names of the original arrays ... in your example.

  2. Base on insight #1":

    char[][] ARRAY_1_AGAIN = ARRAYS[0];
System.out.println(ARRAY_1 == ARRAY_1_AGAIN);  // prints true

    Since ARRAY_1 is the first subarray of ARRAY (as per the previous example), we need to use ARRAYS[0] (not ARRAYS[0]) to access it.

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1 Comment

How would I call the arrays individually again later on?
1

Try this:

List<char[][]> list = new ArrayList<>();
list.add(ARRAY_1);
list.add(ARRAY_2);

Or

char[][][] ARRAY = new char[length][][];
ARRAY[0] = ARRAY_1;
ARRAY[1] = ARRAY_2;

Or

char[][][] ARRAY = new char[][][]{ARRAY_1, ARRAY_2};

Further reading:

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0

You are using a Jagged Array...

Also try this

char[][] array = new char[5][];

array[0] = array1;
array[1] = array2;

Regards

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