Arrays In Java With Example

// SOLVING THIS WITH AN AI ASSISTANT (2026)

If you are working through this problem with an AI coding assistant — Claude, ChatGPT, Cursor chat, Gemini, GitHub Copilot, Aider, or any agent — the goal isn’t to ask for the answer. It is to use the tool to understand the pattern. The prompt sequence I’d run:

Spec it back to me first. “In your own words, what is this problem actually testing? What’s the smallest example that fails the naive approach?”
Brute-force first, optimize after. “Write the simplest correct solution, even if it’s O(n²). Don’t optimize. Just make it correct, with comments explaining each step.”
Ask for the upgrade. “Now show me the optimal solution. What insight makes it possible? What pattern is this an instance of?”
Stress-test it. “Generate 10 edge cases — empty input, single element, duplicates, max size, sorted, reverse-sorted. Run my solution against each.”

The pattern matters more than the answer. If the agent just hands you optimized code, you’ve trained yourself to lose interviews.

The array is a data structure provided by Java which holds elements of the same data type with a fixed size.

An array can hold elements/ values of the same data type, an example being we can create an array that can store 100 elements of type either int/String/char etc.. We can not have array hold multiple datatypes like shown below.

Example 1: [1,2,3,4,5] | [‘a’,’b’,’c’,’d’] (correct)
Example 2: [1, ‘b’,3,’c’] (in correct)

Array Declaration

dataType arrayName[] = new dataType[size];
OR
datatType arrayName[] = [value1, value2, value3];

dataType can be any data types like int, char, float, double, String, etc.. or can be a user-defined data type like a User object.

Example:

int intArray[] = new int[10];

In the above declaration, we declared an int array of size 10, which means it can hold 10 int values. similarly, the below declaration holds 50 char values.

char charArray[] = new char[50];

Indexing

In an array, the index starts with 0 (zero), for example, let’s take the array

int[] a = {4,3,2,1};

a[0] returns the first element in the array i.e 4. similarly a[1] would return the second 3 and a[2] would return the third element 2.

Array Index

Code Example

class ArrayExample {
    public static void main(String [] args) {
              int[] num = new int[5];
              num[0] = 4;
              num[1] = 5;
              num[2] = 7;
              num[3] = 9;
              num[4] = 3;
              
             for(int i= 0; i<num.length; i++) {
                System.out.println("Array element at index "+i+" = "+num[i]);
            }
        }
}

The resultant output for the above example would be

Array element at index 0 = 4
Array element at index 1 = 5
Array element at index 2 = 7
Array element at index 3 = 9
Array element at index 4 = 3

Here is the video explanation of an Array in Java.

Happy Coding!…

For the AI-native engineering side of HackerHeap — building MCP servers, comparing agents (Claude Code, Cursor, Windsurf, Codex, Gemini, Copilot), and weekly working code — see the Friday Build newsletter and the MCP archive.

rajendra