How to print an array in Java in a readable format?

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1

How to print an array in Java in a readable format?

In Java, arrays don’t override toString(), so printing an array directly results in output like className + '@' + hex hashCode, as defined by Object.toString():

int[] intArray = new int[] {1, 2, 3, 4, 5};
System.out.println(intArray); // Prints something like '[I@3343c8b3'

But typically, we’d want output like [1, 2, 3, 4, 5]. How to print an array in Java in a simple and readable way? Here are some example inputs and expected outputs:

// Array of primitives:
int[] intArray = {1, 2, 3, 4, 5};
// Expected output: [1, 2, 3, 4, 5]

// Array of object references:
String[] strArray = {"John", "Mary", "Bob"};
// Expected output: [John, Mary, Bob]
2

From my experience, the easiest way to print an array in Java in a readable format is by using Arrays.toString(). It’s simple, effective, and works with both primitive arrays and object arrays.

Here’s an example:

import java.util.Arrays;

public class PrintArray {
    public static void main(String[] args) {
        int[] intArray = {1, 2, 3, 4, 5};
        System.out.println(Arrays.toString(intArray)); // [1, 2, 3, 4, 5]

        String[] strArray = {"John", "Mary", "Bob"};
        System.out.println(Arrays.toString(strArray)); // [John, Mary, Bob]
    }
}

:white_check_mark: Pros:

  • Works with primitive arrays and object arrays.
  • It’s a simple one-liner.
  • Produces readable output.

It’s a solid go-to for most cases when you need to print an array in Java in a quick and straightforward way.

3

Definitely agree with @yanisleidi-rodriguez Arrays.toString() is great, but it won’t handle multi-dimensional arrays very well. You’ll see something like [I@hashcode, which isn’t all that helpful.

If you’re working with multi-dimensional arrays, I’d recommend using Arrays.deepToString() instead. Here’s how you can use it:

import java.util.Arrays;

public class PrintMultiArray {
    public static void main(String[] args) {
        int[][] multiArray = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };

        System.out.println(Arrays.deepToString(multiArray)); // [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    }
}

:small_blue_diamond: Output: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

:white_check_mark: Pros:

  • Handles multi-dimensional arrays.
  • Outputs in a clean, structured format.

So if you’re dealing with something more complex than a flat array, this will do the trick for how to print an array in Java."

4

You’re right, @ian-partridge But if you want even more flexibility, like when you need a custom format, such as {1, 2, 3, 4, 5} instead of the default [1, 2, 3, 4, 5], Java Streams are a great option. You can use them to format the array exactly the way you need.

Check this out:

import java.util.Arrays;
import java.util.stream.Collectors;

public class PrintWithStreams {
    public static void main(String[] args) {
        int[] intArray = {1, 2, 3, 4, 5};

        String formatted = Arrays.stream(intArray)
                                 .mapToObj(String::valueOf)
                                 .collect(Collectors.joining(", ", "{", "}"));

        System.out.println(formatted); // {1, 2, 3, 4, 5}
    }
}

:white_check_mark: Pros:

  • Fully customizable format.
  • Works great for logging or when you need outputs similar to JSON formatting.

It’s a super handy tool if you’re looking for more control over how to print an array in Java, especially for specific formatting or when you want a cleaner, more visually distinct output.