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

Why do we need the Java 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

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 class Arrays extends Object

To use Arrays,

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

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]

Note: When asList() is used with primitive arrays, it shows the memory reference of the array instead of the list contents. This happens because the asList() method returns a fixed-size list backed by the original array, and for primitive types like int[], it treats the array as an object, not as a list of values.

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

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

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

Below table contains list of all methods: