How do I declare and initialize an array in Java?

Create an Array with Specific Numbers

You can populate your array with a sequence of numbers. All Hail IntStream :

int[] startFromZero = IntStream.range(0, 10).toArray(); // Because the world started counting from zero.


Need an inclusive range ?

int[] inclusive = IntStream.rangeClosed(1, 10).toArray(); // We like everyone.


For our selective folks, here's you can add specific values into an array :

int[] choosy = IntStream.of(12, 34, 56).toArray(); // Pick and mix.


Some people like it sorted, well here you go:

int[] sorted = IntStream.of(12, 9, 21).sorted().toArray();  // Neat freaks got their cover.


The Matrix Revisited: Multidimensional Arrays

Creating a two-dimensional array is easier than you think:

int[][] matrix = {
  {1, 2, 3},
  {4, 5, 6},
  {7, 8, 9}
}; // Who needs effects when you can have Matrix in console?


If your sub-arrays fancy different sizes, make it a ragged array:

int[][] raggedArray = {
  {1, 2},
  {3, 4, 5},
  {6, 7, 8, 9}
}; // When sub-arrays can't agree on sizes...


Shake it up: Common Operations and Utilities

The java.util.Arrays class is your Swiss army knife. Want to fill the array but too lazy to type:

Arrays.fill(myArray, 42); // When you're feeling 42ish.


Clone wars? Here's how to copy arrays:

int[] cloneArmy = Arrays.copyOf(originalArray, newLength); // Originality is overrated anyway.


Are these twins or mirror images? Compare arrays:

boolean dittoMove = Arrays.equals(arr1, arr2); // Pokémon reference


And to talk your array into being a string:

String arrayInDisguise = Arrays.toString(myIntArray); // Array's undercover mission.


Syntax Surfers

Java caters to your syntax preferences. Fancy cursive or print, it got you:

int[] arraySyntax1; // More in vogue
int arraySyntax2[]; // Throwback to the C era


Array Declaring and Initializing: Best Practices

When declaring the size of an array, remember it's also the max number of elements it can hold. Also, over-declaring sizes may result in wasting memory. Happy Earth day:

int[] overkillArray = new int[100]; // Too much of anything is bad.


Initializing with values is the speed racer way but may lead to scalability issues:

int[] fixedArray = {1, 2, 3}; // Manual labor in the age of automation!


The separate declaration and initialization waltz can lead to code clarity. Especially in areas with fat codebases:

int[] array; // Sailors preparing the ship
// Monster octopus in the sea aka lot of code
array = new int[] {3, 6, 9}; // Cannonballs loaded, fire!
