Arrays Class in Java

The Arrays class in java.util is a utility class that provides static methods to perform operations like sorting, searching, comparing, and converting arrays. It cannot be instantiated and is used only for utility purposes.

• Provides static methods such as sort(), binarySearch(), equals(), toString()
• Implicitly extends Object and is not meant to be instantiated

Class Declaration

Arrays is a final utility class in java.util package that extends Object class, which is the root of the Java class hierarchy

public final class Arrays

To use Arrays,

Arrays.<function name>;
Arrays.sort(array_name);

Why do we need Arrays class

Java provides a utility class called java.util.Arrays to help developers perform common array operations easily and efficiently. like:

• Fill an array with a particular value.
• Sort an array
• Search in an array
• And many more

Methods in Java Array Class 

The Arrays class of the java.util package contains several static methods that can be used to fill, sort, search, etc in arrays. Let's take a look at methods and their implementation:

1. asList() method.

This method converts an array into a list.

import java.util.Arrays;

class Geeks{
  
    public static void main(String[] args){
        // Get the Array
        int intArr[] = { 10, 20, 15, 22, 35 };

        // To convert the elements as List
        System.out.println("int Array as List: "
                           + Arrays.asList(intArr));
    }
}

Integer Array as List: [[I@19469ea2]

Explanation: This method converts an array into a fixed-size list using Arrays.asList(). It works properly with object arrays (like Integer, String), but with primitive arrays, the whole array becomes a single list element instead of individual values.

Note: asList() does not work properly with primitive arrays (like int[], char[]). It treats the entire array as a single element instead of converting each value into a list.

2. binarySearch() Method

This methods search for the specified element in the array with the help of the binary search algorithm.

import java.util.Arrays;

public class Geeks {

    public static void main(String[] args){

        // Get the Array
        int intArr[] = { 10, 20, 15, 22, 35 };

        Arrays.sort(intArr);

        int intKey = 22;

        // Print the key and corresponding index
        System.out.println(
            intKey + " found at index = "
            + Arrays.binarySearch(intArr, intKey));
    }
}

22 found at index = 3

Explanation: This method searches an element in a sorted array using binary search. If the element is found, it returns its index; otherwise, it returns a negative value indicating the insertion point.

3. binarySearch(array, fromIndex, toIndex, key, Comparator) Method 

This method searches a range of the specified array for the specified object using the binary search algorithm.

import java.util.Arrays;

public class Main {
    public static void main(String[] args)
    {

        // Get the Array
        int intArr[] = { 10, 20, 15, 22, 35 };

        Arrays.sort(intArr);

        int intKey = 22;

        System.out.println(
            intKey
            + " found at index = "
            + Arrays
                  .binarySearch(intArr, 1, 3, intKey));
    }
}

22 found at index = -4

Explanation: This method searches for an element within a specified range of the array using a comparator. It is useful for custom sorting logic or partial array searching.

4. compare(array 1, array 2) Method 

This method returns the difference as an integer lexicographically.

import java.util.Arrays;

public class Main {
    public static void main(String[] args)
    {

        // Get the Array
        int intArr[] = { 10, 20, 15, 22, 35 };

        // Get the second Array
        int intArr1[] = { 10, 15, 22 };

        // To compare both arrays
        System.out.println("int Arrays on comparison: "
                           + Arrays.compare(intArr, intArr1));
    }
}

Integer Arrays on comparison: 1

Explanation: This method compares two arrays lexicographically. It returns 0 if arrays are equal, a negative value if the first array is smaller, and a positive value if the first array is greater.

Methods of Array Class

Below table contains list of all methods