Java Arrays Basics

Arrays in Java

Arrays in Java are non-primitive data types that store elements of a similar data type in the memory. Arrays can store both primitive and non-primitive data types. There are two types of arrays: single-dimensional and multi-dimensional.

Single-Dimensional Arrays

In Java, a single-dimensional array can be defined as follows:

type var-name[];

where type declares the element type of the array, and var-name is the name of the array. For example:

int[] numbers;

Multi-Dimensional Arrays

A multi-dimensional array contains other arrays. In Java, you can create multi-dimensional arrays with two or more dimensions. The syntax is:

type[][] var-name;

For example:

int[][] matrix;

Creating Arrays

Arrays in Java are dynamically allocated, which means that the memory is allocated when the array is created. This can be done using the new keyword:

var-name = new type[size];

For example:

int[] numbers = new int;

Here, type specifies the type of data being allocated, size determines the number of elements in the array, and var-name is the name of the array variable.

Array Literals

Array literals can be used when the size of the array and the variables of the array are already known. For example:

int[] numbers = {1, 2, 3, 4, 5};

Array Access

In a Java array, the index always starts from 0 and ends at (total array size)-1. All the elements of an array can be accessed using a for loop:

for (int i = 0; i < numbers.length; i++) {
    System.out.println(numbers[i]);
}

In this code, numbers is the array, and numbers.length is the length of the array. The for loop iterates over the elements of the array, and numbers[i] accesses the element at index i.

Array Copying

Arrays can be copied using the clone() method:

int[] copiedNumbers = numbers.clone();

Array Sorting

Arrays can be sorted using the Arrays.sort() method:

Arrays.sort(numbers);

Array Operations

Arrays in Java support various operations such as adding, removing, and modifying elements. For example, to add an element to an array:

numbers[numbers.length] = 6;

To remove an element from an array:

numbers[numbers.length-1] = 0;

Array Cloning

Arrays can be cloned using the clone() method:

int[] clonedNumbers = numbers.clone();

Array Initialization

Arrays can be initialized using the Arrays.fill() method:

Arrays.fill(numbers, 0, 2, 10);

In this code, Arrays.fill() sets the elements from index 0 to 2 in the numbers array to the value 10.

Array Iteration

Arrays can be iterated using the for-each loop:

for (int number : numbers) {
    System.out.println(number);
}

In this code, number is the variable that holds the value of each element in the numbers array, and numbers is the array.

Array Comparison

Arrays can be compared using the Arrays.equals() method:

if (Arrays.equals(numbers, clonedNumbers)) {
    System.out.println("Arrays are equal");
}

In this code, Arrays.equals() compares the numbers and clonedNumbers arrays.

Array Storage

Arrays in Java are stored in memory. The elements of an array are stored in contiguous memory locations:

int[] numbers = {1, 2, 3, 4, 5};
System.out.println(numbers + " " + numbers + " " + numbers + " " + numbers + " " + numbers);

In this code, numbers represents the first element of the array (1), numbers represents the second element of the array (2), and so on.

Array Sizing

Arrays in Java have a fixed size, which means that the size of an array cannot be changed once it is declared:

int[] numbers = new int;

In this code, numbers is an array of integers with a size of 5.

Array Null Check

Arrays can be checked for null using the Arrays.isEmpty() method:

if (Arrays.isEmpty(numbers)) {
    System.out.println("Array is empty");
}

In this code, Arrays.isEmpty() checks if the numbers array is empty.

Array Flattening

Arrays can be flattened using the Arrays.stream() method:

Arrays.stream(numbers).forEach(System.out::println);

In this code, Arrays.stream() creates a stream from the numbers array, and forEach() iterates over the elements of the stream and prints them.

Array Stream Operations

Arrays can be operated on using the Arrays.stream() method:

Arrays.stream(numbers).filter(n -> n % 2 == 0).forEach(System.out::println);

In this code, Arrays.stream() creates a stream from the numbers array, filter() filters out the even numbers, and forEach() prints them.

Array Shuffling

Arrays can be shuffled using the Arrays.shuffle()

This quiz covers the fundamentals of working with arrays in Java, including the declaration of single-dimensional and multi-dimensional arrays, array initialization, copying, sorting, operations, comparison, storage, and stream operations like iteration, flattening, filtering, and shuffling.