Array

Array in Java

Overview

An array in Java is a data structure that can hold multiple values of the same type. Arrays in Java are zero-indexed, meaning the first element is accessed at index 0. Once the size of an array is defined, it cannot be changed.

---

Characteristics of Arrays

Feature	Details
Package	java.lang
Fixed Size	The size of an array is fixed once initialized.
Indexed	Elements are accessed using an index.
Default Values	Numeric types default to 0, boolean defaults to false, and object references to null.

---

Key Features of Arrays

• Fixed Size: Once an array is initialized, its size cannot be changed.
• Zero-Indexing: Arrays are zero-indexed, meaning the first element is accessed at index 0.
• Homogeneous Elements: All elements in an array are of the same data type.
• Memory Efficiency: Arrays are efficient in terms of memory storage for large amounts of data.

---

Operations on Array Types

Array Operations

Operation	Symbol	Example
Accessing Elements	[]	arr[0]
Length of Array	.length	arr.length
Initializing Array	new	type[] arr = new type[5];     eg:-         int[] arr = new int[5];         double[] arr = new double[5];         String[] arr = new String[5];
Iterating over Array	for-each	for (int num : arr) {       System.out.println(num); }

---

Static Methods

int arr[] = {20, 41, 3, 23}; // Use this as an example

int arr_2[] = new int[3]; // Empty array

Method	Description	Return Type	Example
copyOf(int[] original, int newLength)	Copies the specified array, truncating or padding with 0 or null.	int[]	Arrays.copyOf(arr, 2);
fill(int[] array, int val)	Fills the array with the specified value.	void	Arrays.fill(arr, 5);
equals(int[] a, int[] b)	Compares two arrays for equality.	boolean	Arrays.equals(arr1, arr2);
sort(int[] a)	Sorts the specified array in ascending order.	void	Arrays.sort(arr);
binarySearch(int[] a, int key)	Searches for a value in a sorted array. Returns the index of the search key, or a negative value if not found.	int	Arrays.binarySearch(arr, 5);
deepToString(Object[] arr)	Returns a string representation of a multidimensional array.	String	Arrays.deepToString(arr);
toString(Object[] arr)	Returns a string representation of the array, using Arrays.toString() to format the array as a string.	String	Arrays.toString(arr);
copyOfRange(T[] arr, int from, int to)	Copies a specified range from the array to a new array.	T[]	Arrays.copyOfRange(arr, 2, 5);
compare(T[] arr1, T[] arr2)	Compares two arrays lexicographically. Returns a negative value if the first array is less than the second, positive if greater, or 0 if equal.	int	Arrays.compare(arr1, arr2);
stream(T[] arr)	Converts the array into a stream, enabling operations like filtering, mapping, and reducing.	Stream<T>	Arrays.stream(arr1);

---

Instance Methods

int arr[] = {20, 41, 3, 23}; // Use this as an example

Method	Description	Return Type	Example	Retuwn Value
length	Returns the length of the array.	int	arr.length;	4 (Length of the array)
clone()	Creates a copy of the array.	Object	arr.clone();	{20, 41, 3, 23} (A new array)
hashCode()	Returns a hash code value for the array.	int	arr.hashCode();	An integer (e.g : 12345678)

---

Example Code

import java.util.Arrays;

public class ArrayExample {
    public static void main(String[] args) {
        // Create an array
        int[] arr = {5, 2, 9, 1, 5, 6};

        // Get the length of the array
        System.out.println("Array length: " + arr.length);

        // Access elements
        System.out.println("Element at index 0: " + arr[0]);

        // Sort the array
        Arrays.sort(arr);
        System.out.println("Sorted array: " + Arrays.toString(arr));

        // Search for an element
        int index = Arrays.binarySearch(arr, 5);
        System.out.println("Index of 5: " + index);

        // Fill the array with a specific value
        Arrays.fill(arr, 0);
        System.out.println("Filled array: " + Arrays.toString(arr));

        // Clone the array
        int[] clonedArray = arr.clone();
        System.out.println("Cloned array: " + Arrays.toString(clonedArray));
    }
}

For more: ArrayDataType.java