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Array Construction

Execution/Test Class

Learn to test custom Array class: verify insert(), remove(), get(), size() operations. Understand capacity vs size differences with practical examples. Complete data structure testing guide for robust code validation.

Let us create an array with capacity as 10 and insert 5 numbers in it, the size of the array becomes 5.

Illustration's

Figure 1 - Array Illustration with capacity of 10 elements
Figure 1 - Array Illustration with capacity of 10 elements

Another illustration that clarifies the difference between capacity and size of the array.

Figure 2 - Array of capacity 10 and size 4 containing 4 elements
Figure 2 - Array of capacity 10 and size 4 containing 4 elements

What do you think is stored in the index 5 to index 9? The answer is zeros.

So 0's are stored from the index 5 to 9. So when you access A[6] you get 0, for A[2] you get 3, and so on.

In the above, we have constructed an Array class and basic operations insert, remove, get, and size etc. Let us test each of the methods to ensure nothing is breaking in our code.

Code

Following is the execution class

package dev.ggorantala.ds.arrays;

public class ArrayExecution {
  private static final int[] INPUT = new int[] {1, 2, 3, 4, 5};

  public static void main(String[] args) {
    Array array = new Array(10);
    for (int value : INPUT) {
      array.insert(value);
    }

    array.remove(2); // removed element `3` from array

    System.out.println(array.get(0)); // 1
    System.out.println(array.size()); // 4

    // The extra o's are because of the array capacity which is 10
    array.print(); // 1, 2, 4, 5, 0, 0, 0, 0, 0, 0
  }
}

Explanation

Array array = new Array(10); creates an array with a capacity 10.

The input array we declared holds 5 elements.

private static final int[] INPUT = new int[] {1, 2, 3, 4, 5};

Using a simple for-loop, we are storing the INPUT data into our newly created array instance variable.

for (int value : INPUT) {
  array.insert(value);
}

We removed an element at the index 2 using array.remove(2);

Finally, we called get, size and print methods to display data on the console.

Hurrah! You just implemented your first data structure in computer science and successfully tested it.