The Arrays class in java.util package is a utility class that provides static methods to perform operations on Java arrays, such as sorting, searching, comparing and converting to strings.
The class hierarchy is as follows:
Arrays class is a utility class in java.util package that extends Object
Array ClassWhy 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:
Java Arrays Class Methods, Explained with Examples
Example 1: asList() method.
This method converts an array into a list.
Java
// Importing Arrays utility class
// from java.util package
import java.util.Arrays;
// Main class
class Geeks {
// Main driver method
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("Integer Array as List: "
+ Arrays.asList(intArr));
}
}
OutputInteger 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.
Example 2: binarySearch() Method
This methods search for the specified element in the array with the help of the binary search algorithm.
Java
import java.util.Arrays;
// Main class
public class Geeks {
// Main driver method
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));
}
}
Output22 found at index = 3
Example 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.
Java
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));
}
}
Output22 found at index = -4
Example 4: compare(array 1, array 2) Method
This method returns the difference as an integer lexicographically.
Java
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("Integer Arrays on comparison: "
+ Arrays.compare(intArr, intArr1));
}
}
OutputInteger Arrays on comparison: 1
Example 5: compareUnsigned(array 1, array 2) Method
This method is used to compare two arrays of primitive int[] values (or other primitive array types) lexicographically, but with the values treated as unsigned integers.
Java
import java.util.Arrays;
public class Main {
public static void main(String[] args)
{
// Get the Arrays
int intArr[] = { 10, 20, 15, 22, 35 };
// Get the second Arrays
int intArr1[] = { 10, 15, 22 };
// To compare both arrays
System.out.println("Integer Arrays on comparison: "
+ Arrays.compareUnsigned(intArr, intArr1));
}
}
OutputInteger Arrays on comparison: 1
Example 6: copyOf(originalArray, newLength) Method
This method is used to copy the elements of an array into a new array of the specified new length.
Java
import java.util.Arrays;
public class Geeks{
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To print the elements in one line
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
System.out.println("\nNew Arrays by copyOf:\n");
System.out.println("Integer Array: "
+ Arrays.toString(
Arrays.copyOf(intArr, 10)));
}
}
OutputInteger Array: [10, 20, 15, 22, 35]
New Arrays by copyOf:
Integer Array: [10, 20, 15, 22, 35, 0, 0, 0, 0, 0]
Example 7: copyOfRange(originalArray, fromIndex, endIndex) Method
This method is used to copy a range of elements from an array into a new array.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To print the elements in one line
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
System.out.println("\nNew Arrays by copyOfRange:\n");
// To copy the array into an array of new length
System.out.println("Integer Array: "
+ Arrays.toString(
Arrays.copyOfRange(intArr, 1, 3)));
}
}
OutputInteger Array: [10, 20, 15, 22, 35]
New Arrays by copyOfRange:
Integer Array: [20, 15]
Example 8: deepEquals(Object[] a1, Object[] a2) Method
This method is used to compare two arrays of objects to check if they are deeply equal.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Arrays
int intArr[][] = { { 10, 20, 15, 22, 35 } };
// Get the second Arrays
int intArr1[][] = { { 10, 15, 22 } };
// To compare both arrays
System.out.println("Integer Arrays on comparison: "
+ Arrays.deepEquals(intArr, intArr1));
}
}
OutputInteger Arrays on comparison: false
Example 9: deepHashCode(Object[] a) Method
This method is used to compute a hash code for an array of objects recursively.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[][] = { { 10, 20, 15, 22, 35 } };
// To get the dep hashCode of the arrays
System.out.println("Integer Array: "
+ Arrays.deepHashCode(intArr));
}
}
OutputInteger Array: 38475344
Example 10: deepToString(Object[] a) Method
This method is used to return a string representation of an array recursively.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[][] = { { 10, 20, 15, 22, 35 } };
// To get the deep String of the arrays
System.out.println("Integer Array: "
+ Arrays.deepToString(intArr));
}
}
OutputInteger Array: [[10, 20, 15, 22, 35]]
Example 11: equals(array1, array2) Method
This method is used to compare two arrays to check if they are equal.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Arrays
int intArr[] = { 10, 20, 15, 22, 35 };
// Get the second Arrays
int intArr1[] = { 10, 15, 22 };
// To compare both arrays
System.out.println("Integer Arrays on comparison: "
+ Arrays.equals(intArr, intArr1));
}
}
OutputInteger Arrays on comparison: false
Example 12: fill(originalArray, fillValue) Method
This method is used to fill an entire array or a subrange of an array with a specific value.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Arrays
int intArr[] = { 10, 20, 15, 22, 35 };
int intKey = 22;
Arrays.fill(intArr, intKey);
// To fill the arrays
System.out.println("Integer Array on filling: "
+ Arrays.toString(intArr));
}
}
OutputInteger Array on filling: [22, 22, 22, 22, 22]
Example 13: hashCode(originalArray) Method
This method is used to compute a hash code for an array
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To get the hashCode of the arrays
System.out.println("Integer Array: "
+ Arrays.hashCode(intArr));
}
}
OutputInteger Array: 38475313
Example 14: mismatch(array1, array2) Method
This method is used to find the index of the first mismatched element between two arrays
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Arrays
int intArr[] = { 10, 20, 15, 22, 35 };
// Get the second Arrays
int intArr1[] = { 10, 15, 22 };
// To compare both arrays
System.out.println("The element mismatched at index: "
+ Arrays.mismatch(intArr, intArr1));
}
}
OutputThe element mismatched at index: 1
Example 15: parallelSort(originalArray) Method
This method is used to sort an array in parallel.
Java
import java.util.Arrays;
// Main class
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To sort the array using parallelSort
Arrays.parallelSort(intArr);
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
}
}
OutputInteger Array: [10, 15, 20, 22, 35]
Example 16: sort(originalArray) Method
This method is used to sort an array in ascending order
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To sort the array using normal sort-
Arrays.sort(intArr);
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
}
}
OutputInteger Array: [10, 15, 20, 22, 35]
Example 17: sort(originalArray, fromIndex, endIndex) Method
This method is used to sort a specified range of an array in ascending order
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To sort the array using normal sort
Arrays.sort(intArr, 1, 3);
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
}
}
OutputInteger Array: [10, 15, 20, 22, 35]
Example 18: sort(T[] a, int fromIndex, int toIndex, Comparator< super T> c) Method
This method is used to sort a specified range of an array using a custom comparator for sorting.
Java
import java.util.*;
import java.lang.*;
import java.io.*;
// A class to represent a student.
class Student {
int rollno;
String name, address;
// Constructor
public Student(int rollno, String name,
String address)
{
this.rollno = rollno;
this.name = name;
this.address = address;
}
// Used to print student details in main()
public String toString()
{
return this.rollno + " "
+ this.name + " "
+ this.address;
}
}
class Sortbyroll implements Comparator<Student> {
// Used for sorting in ascending order of
// roll number
public int compare(Student a, Student b)
{
return a.rollno - b.rollno;
}
}
// Driver class
class Geeks {
public static void main(String[] args)
{
Student[] arr = { new Student(111, "bbbb", "london"),
new Student(131, "aaaa", "nyc"),
new Student(121, "cccc", "jaipur") };
System.out.println("Unsorted");
for (int i = 0; i < arr.length; i++)
System.out.println(arr[i]);
Arrays.sort(arr, 1, 2, new Sortbyroll());
System.out.println("\nSorted by rollno");
for (int i = 0; i < arr.length; i++)
System.out.println(arr[i]);
}
}
OutputUnsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur
Sorted by rollno
111 bbbb london
131 aaaa nyc
121 cccc jaipur
Example 19: sort(T[] a, Comparator< super T> c) Method
This method is used to sort an entire array of objects (T[]) using a custom comparator (Comparator<? super T>).
Java
import java.util.*;
import java.lang.*;
import java.io.*;
// A class to represent a student.
class Student {
int rollno;
String name, address;
// Constructor
public Student(int rollno, String name,
String address)
{
this.rollno = rollno;
this.name = name;
this.address = address;
}
// Used to print student details in main()
public String toString()
{
return this.rollno + " "
+ this.name + " "
+ this.address;
}
}
class Sortbyroll implements Comparator<Student> {
// Used for sorting in ascending order of roll number
public int compare(Student a, Student b)
{
return a.rollno - b.rollno;
}
}
// Driver class
class Geeks {
public static void main(String[] args)
{
Student[] arr = { new Student(111, "bbbb", "london"),
new Student(131, "aaaa", "nyc"),
new Student(121, "cccc", "jaipur") };
System.out.println("Unsorted");
for (int i = 0; i < arr.length; i++)
System.out.println(arr[i]);
Arrays.sort(arr, new Sortbyroll());
System.out.println("\nSorted by rollno");
for (int i = 0; i < arr.length; i++)
System.out.println(arr[i]);
}
}
OutputUnsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur
Sorted by rollno
111 bbbb london
121 cccc jaipur
131 aaaa nyc
Example 20: spliterator(originalArray) Method
This method is used to create a Spliterator for the given array.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To sort the array using normal sort
System.out.println("Integer Array: "
+ Arrays.spliterator(intArr));
}
}
OutputInteger Array: java.util.Spliterators$IntArraySpliterator@4e50df2e
Example 21: spliterator(originalArray, fromIndex, endIndex) Method
This method is used to create a Spliterator for a subrange of the given array, starting from fromIndex (inclusive) to toIndex (exclusive).
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To sort the array using normal sort
System.out.println("Integer Array: "
+ Arrays.spliterator(intArr, 1, 3));
}
}
OutputInteger Array: java.util.Spliterators$IntArraySpliterator@4e50df2e
Example 22: stream(originalArray) Method
This method is used to convert an array into a stream.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To get the Stream from the array
System.out.println("Integer Array: "
+ Arrays.stream(intArr));
}
}
OutputInteger Array: java.util.stream.IntPipeline$Head@7291c18f
Example 23: toString(originalArray) Method
This method is used to convert an array into a human-readable string representation.
Java
import java.util.Arrays;
public class Geeks {
public static void main(String[] args)
{
// Get the Array
int intArr[] = { 10, 20, 15, 22, 35 };
// To print the elements in one line
System.out.println("Integer Array: "
+ Arrays.toString(intArr));
}
}
OutputInteger Array: [10, 20, 15, 22, 35]
Below table contains list of all methods:
| Methods | Action Performed |
|---|
| asList() | Returns a fixed-size list backed by the specified Arrays |
| binarySearch() | Searches for the specified element in the array with the help of the Binary Search Algorithm |
| binarySearch(array, fromIndex, toIndex, key, Comparator) | Searches a range of the specified array for the specified object using the Binary Search Algorithm |
| compare(array 1, array 2) | Compares two arrays passed as parameters lexicographically. |
| copyOf(originalArray, newLength) | Copies the specified array, truncating or padding with the default value (if necessary) so the copy has the specified length. |
| copyOfRange(originalArray, fromIndex, endIndex) | Copies the specified range of the specified array into a new Arrays. |
| deepEquals(Object[] a1, Object[] a2) | Returns true if the two specified arrays are deeply equal to one another. |
| deepHashCode(Object[] a) | Returns a hash code based on the "deep contents" of the specified Arrays. |
| deepToString(Object[] a) | Returns a string representation of the "deep contents" of the specified Arrays. |
| equals(array1, array2) | Checks if both the arrays are equal or not. |
| fill(originalArray, fillValue) | Assigns this fill value to each index of this arrays. |
| hashCode(originalArray) | Returns an integer hashCode of this array instance. |
| mismatch(array1, array2) | Finds and returns the index of the first unmatched element between the two specified arrays. |
| parallelPrefix(originalArray, fromIndex, endIndex, functionalOperator) | Performs parallelPrefix for the given range of the array with the specified functional operator. |
| parallelPrefix(originalArray, operator) | Performs parallelPrefix for complete array with the specified functional operator. |
| parallelSetAll(originalArray, functionalGenerator) | Sets all the elements of this array in parallel, using the provided generator function. |
| parallelSort(originalArray) | Sorts the specified array using parallel sort. |
| setAll(originalArray, functionalGenerator) | Sets all the elements of the specified array using the generator function provided. |
| sort(originalArray) | Sorts the complete array in ascending order. |
| sort(originalArray, fromIndex, endIndex) | Sorts the specified range of array in ascending order. |
| sort(T[] a, int fromIndex, int toIndex, Comparator< super T> c) | Sorts the specified range of the specified array of objects according to the order induced by the specified comparator. |
| sort(T[] a, Comparator< super T> c) | Sorts the specified array of objects according to the order induced by the specified comparator. |
| spliterator(originalArray) | Returns a Spliterator covering all of the specified Arrays. |
| spliterator(originalArray, fromIndex, endIndex) | Returns a Spliterator of the type of the array covering the specified range of the specified arrays. |
| stream(originalArray) | Returns a sequential stream with the specified array as its source. |
| toString(originalArray) | It returns a string representation of the contents of this array. The string representation consists of a list of the array’s elements, enclosed in square brackets (“[]”). Adjacent elements are separated by the characters a comma followed by a space. Elements are converted to strings as by String.valueOf() function. |
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