3-Dimensional Array in Java 3 Level.md

3-Dimensional Array in Java — 3 LEVEL

Think of a 3-D array as multiple 2-D tables stacked together.

1-D → Line 2-D → Table 3-D → Collection of Tables / Layers

---

🟢 LEVEL 1 — BEGINNER

1. What is a 3-Dimensional Array?

A 3-Dimensional Array stores data using three indexes.

int[][][] a;

Access an element using:

a[layer][row][column]

Remember:

a[i][j][k] │ │ │ │ │ └── Column │ └───── Row └──────── Layer

---

2. Simple Example

int[][][] a = { { {10, 20}, {30, 40} }, { {50, 60}, {70, 80} } };

Visualize:

Layer 0 Layer 1

10 20 50 60 30 40 70 80

There are:

2 Layers 2 Rows per Layer 2 Columns per Row

Total elements:

2 × 2 × 2 = 8

---

3. Accessing Elements

System.out.println(a[0][0][0]);

Output:

10

Because:

0 → Layer 0 0 → Row 0 0 → Column 0

Another example:

System.out.println(a[1][0][1]);

Output:

60

---

4. Declaration and Creation

Declaration:

int[][][] a;

Creation:

a = new int[2][3][4];

Or together:

int[][][] a = new int[2][3][4];

Meaning:

2 → Layers 3 → Rows 4 → Columns

---

🟡 LEVEL 2 — INTERMEDIATE

1. length in 3-D Arrays

For:

int[][][] a = new int[2][3][4];

Number of layers

a.length

→ 2

Number of rows

a[i].length

→ 3

Number of columns

a[i][j].length

→ 4

So memorize:

a.length ↓ Layers

a[i].length ↓ Rows

a[i][j].length ↓ Columns

---

2. Traversing a 3-D Array

Because there are three dimensions, we normally use three nested loops.

for (int i = 0; i < a.length; i++) {

for (int j = 0; j < a[i].length; j++) {

    for (int k = 0; k < a[i][j].length; k++) {

        System.out.print(a[i][j][k] + " ");
    }

    System.out.println();
}

System.out.println();

}

Roles:

i → Layer j → Row k → Column

---

3. Complete Program

class ThreeDArray {

public static void main(String[] args) {

    int[][][] a = {
        {
            {10, 20},
            {30, 40}
        },
        {
            {50, 60},
            {70, 80}
        }
    };

    for (int i = 0; i < a.length; i++) {

        for (int j = 0; j < a[i].length; j++) {

            for (int k = 0; k < a[i][j].length; k++) {

                System.out.print(a[i][j][k] + " ");
            }

            System.out.println();
        }

        System.out.println();
    }
}

}

Output:

10 20 30 40

50 60 70 80

---

4. Sum of All Elements

int sum = 0;

for (int i = 0; i < a.length; i++) {

for (int j = 0; j < a[i].length; j++) {

    for (int k = 0; k < a[i][j].length; k++) {

        sum += a[i][j][k];
    }
}

}

System.out.println("Sum = " + sum);

For the above array:

10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 = 360

---

🔴 LEVEL 3 — ADVANCED

1. 3-D Array Is an Array of Arrays of Arrays

This is the most important advanced concept.

When you write:

int[][][] a;

think:

int[][][] ↓ Array of ↓ int[][] ↓ Array of ↓ int[] ↓ Array of ↓ int

So:

a │ ├── Layer 0 → int[][] │ ├── Row 0 → int[] │ └── Row 1 → int[] │ └── Layer 1 → int[][] ├── Row 0 → int[] └── Row 1 → int[]

This is why Java allows jagged 3-D arrays.

---

2. Jagged 3-D Array

Rows don't have to contain the same number of elements.

int[][][] a = { { {10, 20}, {30, 40, 50} }, { {60}, {70, 80, 90} } };

Structure:

Layer 0 Row 0 → 10 20 Row 1 → 30 40 50

Layer 1 Row 0 → 60 Row 1 → 70 80 90

This is valid because each row is a separate int[].

---

3. Why Use a[i][j].length?

Because rows can have different lengths.

Correct:

for (int i = 0; i < a.length; i++) {

for (int j = 0; j < a[i].length; j++) {

    for (int k = 0; k < a[i][j].length; k++) {

        System.out.println(a[i][j][k]);
    }
}

}

The three limits correspond to the three levels:

a.length ↓ Layer count

a[i].length ↓ Row count

a[i][j].length ↓ Element count

---

⭐ 3-LEVEL MEMORY MAP

3-D ARRAY │ ↓ int[][][] a │ ┌──────────┴──────────┐ ↓ ↓ LEVEL 1 LEVEL 2 Beginner Intermediate │ │ ↓ ↓ Layer/Row/Column length a[i][j][k] nested loops declaration sum/search │ └──────────┬──────────┘ ↓ LEVEL 3 Advanced │ ↓ Array of Arrays │ ↓ Jagged 3-D Array

🔥 Final Formula

int[][][] a = new int[2][3][4];

a.length → 2 → Layers a[i].length → 3 → Rows a[i][j].length → 4 → Columns

a[i][j][k] ↓ ↓ ↓ Layer Row Column

One-line definition

A 3-Dimensional Array in Java is an array of 2-Dimensional arrays that stores data using three indexes: layer, row, and column.