Java - How to iterate through 3-dimensional ArrayList?

Question

I'm trying to implement ArrayList for my project, but I had some problem on the way. If anyone can help me, that would be wonderful.

I have this 3-dimensional array of string, iterated through it to have it hold some String values.

for(int x=0;x<array.length;x++){
  for(int y=0;y<array[0].length;y++){
    for(int z=0;z<array[0][0].length;z++){
       array[x][y][z] = "Lorem ipsum";
    }
  } 
}

But due to its flexibility of size, I've decided to use ArrayList instead.

The problem is, I have no idea how to iterate through a 3-dimensional ArrayList. Thought something like this would work, but it didn't.

ArrayList<ArrayList<ArrayList<String>>> arrSup = new ArrayList<ArrayList<ArrayList<String>>>();

for(int x=0;x<arrSup.size();x++){
  for(int y=0;y<arrSup[0].size();y++){
    for(int z=0;z<arrSup[0][0].size();z++){
       array[x][y][z] = "Lorem ipsum";
    }
  } 
}

So, can anyone tell me how to iterate through a 3-dimensional ArrayList?

Thank you.

In Java 7 (and above) you can simplify the declaration into List<List<List<String>>> arrSup = new ArrayList<>(); thanks to the diamond operator. — Mick Mnemonic
– Mick Mnemonic, Commented Sep 29, 2015 at 17:53

mbinette · Accepted Answer · 2015-09-29 17:46:43Z

1

Use ArrayList::get(int index) and ArrayList::set(int index, T value):

int INITIAL_X_SIZE = 100;
int INITIAL_Y_SIZE = 100;
int INITIAL_Z_SIZE = 100;
ArrayList<ArrayList<ArrayList<String>>> arrSup = new ArrayList<ArrayList<ArrayList<String>>>(INITIAL_X_SIZE);

// Initialize the ArrayLists:
for(int x = 0; x < INITIAL_X_SIZE; x++) {
  arrSup.set(x, new ArrayList<ArrayList<String>>(INITIAL_Y_SIZE));
  for(int y = 0;y < INITIAL_Y_SIZE; y++) {
    arrSup.get(x).set(x, new ArrayList<String>(INITIAL_Z_SIZE));
  }
}

// Iterate through it and do whatever you want to do:
for(int x = 0; x < arrSup.size(); x++) {
  for(int y = 0; y < arrSup.get(x).size(); y++) {
    for(int z = 0; z<arrSup.get(x).get(y).size(); z++) {
       array.get(x).get(y).set(z, "Lorem ipsum");
    }
  } 
}

answered Sep 29, 2015 at 17:46

mbinette

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Comments

Niki van Stein · Accepted Answer · 2015-09-29 17:50:04Z

0

You need to use get there is no indexing for arrayList.

ArrayList<ArrayList<ArrayList<String>>> arrSup = new ArrayList<ArrayList<ArrayList<String>>>();

for(int x=0;x<arrSup.size();x++){
  for(int y=0;y<arrSup.get(0).size();y++){
    for(int z=0;z<arrSup.get(0).get(0).size();z++){
       array.get(x).get(y).set(z, "Lorem ipsum");
    }
  } 
}

answered Sep 29, 2015 at 17:50

Niki van Stein

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1 Comment

Niki van Stein Over a year ago

Changed it, also noticed.

Hong Duan · Accepted Answer · 2015-09-29 17:53:34Z

0

Suppose a 10x10x10 array:

    ArrayList<ArrayList<ArrayList<String>>> arrSup = new ArrayList<ArrayList<ArrayList<String>>>();

    for (int x = 0; x < 10; x++) {
        arrSup.add(new ArrayList<ArrayList<String>>());
        for (int y = 0; y < 10; y++) {
            arrSup.get(x).add(new ArrayList<String>());
            for (int z = 0; z < 10; z++) {
                arrSup.get(x).get(y).add("Lorem ipsum");
            }
        }
    }

answered Sep 29, 2015 at 17:53

Hong Duan

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Comments

Andreas · Accepted Answer · 2015-09-29 17:57:34Z

Unlike multi-dimensional arrays, Lists are not allocated for you, so you have to add the sub-Lists yourself.

Iterating can be done in two ways, depending of whether you need to coordinates.

// Build matrix
final int SIZE_X = 10;
final int SIZE_Y = 10;
final int SIZE_Z = 10;
List<List<List<String>>> matrix = new ArrayList<>();
for (int x = 0; x < SIZE_X; x++) {
    List<List<String>> yList = new ArrayList<>();
    matrix.add(yList);
    for (int y = 0; y < SIZE_Y; y++) {
        List<String> zList = new ArrayList<>();
        yList.add(zList);
        for (int z = 0; z < SIZE_Z; z++)
            zList.add("Lorem ipsum");
    }
}

// Iterate matrix without coordinates
for (List<List<String>> yList : matrix)
    for (List<String> zList : yList)
        for (String value : zList) {
            System.out.println(value);
        }

// Iterate matrix with coordinates
for (int x = 0; x < matrix.size(); x++) {
    List<List<String>> yList = matrix.get(x);
    for (int y = 0; y < yList.size(); y++) {
        List<String> zList = yList.get(y);
        for (int z = 0; z < zList.size(); z++) {
            String value = zList.get(z);
            System.out.println(value);
        }
    }
}

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