Arrays class in Java

Difficulty Level : Easy
Last Updated : 24 Apr, 2019

The Arrays class in java.util package is a part of the Java Collection Framework. This class provides static methods to dynamically create and access Java arrays. It consists of only static methods and the methods of Object class. The methods of this class can be used by the class name itself.

Class Hierarchy:

java.lang.Object
 ↳ java.util.Arrays

Class Declaration:

public class Arrays
    extends Object

Syntax to use Array:

Arrays.<function name>;

Need for the Java-Arrays Class:
There are often times when loops are used to do some tasks on an array like:

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

Arrays class provides several static methods that can be used to perform these tasks directly without the use of loops.

Methods in Java Array:

The Arrays class of the java.util package contains several static methods that can be used to fill, sort, search, etc in arrays. These are:

static <T> List<T> asList(T… a): This method returns a fixed-size list backed by the specified Arrays.

// Java program to demonstrate 
// Arrays.asList() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array as List: [[I@232204a1]

static int binarySearch(elementToBeSearched): These methods searches for the specified element in the array with the help of Binary Search algorithm.

// Java program to demonstrate 
// Arrays.binarySearch() method 
  
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, intKey)); 
    } 
} 

Output:

22 found at index = 3

static <T> int binarySearch(T[] a, int fromIndex, int toIndex, T key, Comparator<T> c): This method searches a range of the specified array for the specified object using the binary search algorithm.

// Java program to demonstrate 
// Arrays.binarySearch() method 
  
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)); 
    } 
} 

Output:

22 found at index = -4

compare(array 1, array 2): This method compares two arrays passed as parameters lexicographically.

// Java program to demonstrate 
// Arrays.compare() method 
  
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)); 
    } 
} 

Output:

Integer Arrays on comparison: 1

compareUnsigned(array 1, array 2): This method compares two arrays lexicographically, numerically treating elements as unsigned.

// Java program to demonstrate 
// Arrays.compareUnsigned() method 
  
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)); 
    } 
} 

Output:

Integer Arrays on comparison: 1

copyOf(originalArray, newLength): This method copies the specified array, truncating or padding with the default value (if necessary) so the copy has the specified length.

// Java program to demonstrate 
// Arrays.copyOf() method 
  
import java.util.Arrays; 
  
public class Main { 
    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))); 
    } 
} 

Output:

Integer Array: [10, 20, 15, 22, 35]

New Arrays by copyOf:

Integer Array: [10, 20, 15, 22, 35, 0, 0, 0, 0, 0]

copyOfRange(originalArray, fromIndex, endIndex): This method copies the specified range of the specified array into a new Arrays.

// Java program to demonstrate 
// Arrays.copyOfRange() method 
  
import java.util.Arrays; 
  
public class Main { 
    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))); 
    } 
} 

Output:

Integer Array: [10, 20, 15, 22, 35]

New Arrays by copyOfRange:

Integer Array: [20, 15]

static boolean deepEquals(Object[] a1, Object[] a2): This method returns true if the two specified arrays are deeply equal to one another.

// Java program to demonstrate 
// Arrays.deepEquals() method 
  
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.deepEquals(intArr, intArr1)); 
    } 
} 

Output:

Integer Arrays on comparison: false

static int deepHashCode(Object[] a): This method returns a hash code based on the “deep contents” of the specified Arrays.

// Java program to demonstrate 
// Arrays.deepHashCode() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: 38475344

static String deepToString(Object[] a): This method returns a string representation of the “deep contents” of the specified Arrays.

// Java program to demonstrate 
// Arrays.deepToString() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: [[10, 20, 15, 22, 35]]

equals(array1, array2): This method checks if both the arrays are equal or not.

// Java program to demonstrate 
// Arrays.equals() method 
  
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.equals(intArr, intArr1)); 
    } 
} 

Output:

Integer Arrays on comparison: false

fill(originalArray, fillValue): This method assigns this fillValue to each index of this Arrays.

// Java program to demonstrate 
// Arrays.fill() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array on filling: [22, 22, 22, 22, 22]

hashCode(originalArray): This method returns an integer hashCode of this array instance.

// Java program to demonstrate 
// Arrays.hashCode() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: 38475313

mismatch(array1, array2): This method finds and returns the index of the first unmatched element between the two specified arrays.

// Java program to demonstrate 
// Arrays.mismatch() method 
  
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("The element mismatched at index: "
                           + Arrays.mismatch(intArr, intArr1)); 
    } 
} 

Output:

The element mismatched at index: 1

parallelPrefix(originalArray, fromIndex, endIndex, functionalOperator): This method performs parallelPrefix for the given range of the array with the specified functional operator.
parallelPrefix(originalArray, operator): This method performs parallelPrefix for complete array with the specified functional operator.
parallelSetAll(originalArray, functionalGenerator): This method set all the elements of this array in parallel, using the provided generator function.

parallelSort(originalArray): This method sorts the specified array using parallel sort.

// Java program to demonstrate 
// Arrays.parallelSort() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: [10, 15, 20, 22, 35]

setAll(originalArray, functionalGenerator): This method sets all the element of the specified array using the generator function provided.

sort(originalArray): This method sorts the complete array in ascending order.

// Java program to demonstrate 
// Arrays.sort() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: [10, 15, 20, 22, 35]

sort(originalArray, fromIndex, endIndex): This method sorts the specified range of array in ascending order.

// Java program to demonstrate 
// Arrays.sort() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: [10, 15, 20, 22, 35]

static <T> void sort(T[] a, int fromIndex, int toIndex, Comparator< super T> c): This method sorts the specified range of the specified array of objects according to the order induced by the specified comparator.

// Java program to demonstrate working of Comparator 
// interface 
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 Main { 
    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]); 
    } 
} 

Output:

Unsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur

Sorted by rollno
111 bbbb london
131 aaaa nyc
121 cccc jaipur

static <T> void sort(T[] a, Comparator< super T> c): This method sorts the specified array of objects according to the order induced by the specified comparator.

// Java program to demonstrate working of Comparator 
// interface 
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 Main { 
    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]); 
    } 
} 

Output:

Unsorted
111 bbbb london
131 aaaa nyc
121 cccc jaipur

Sorted by rollno
111 bbbb london
121 cccc jaipur
131 aaaa nyc

spliterator(originalArray): This method returns a Spliterator covering all of the specified Arrays.

// Java program to demonstrate 
// Arrays.spliterator() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: java.util.Spliterators$IntArraySpliterator@232204a1

spliterator(originalArray, fromIndex, endIndex): This method returns a Spliterator of the type of the array covering the specified range of the specified Arrays.

// Java program to demonstrate 
// Arrays.spliterator() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: java.util.Spliterators$IntArraySpliterator@232204a1

stream(originalArray): This method returns a sequential stream with the specified array as its source.

// Java program to demonstrate 
// Arrays.stream() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: java.util.stream.IntPipeline$Head@4aa298b7

toString(originalArray): This method returns a String representation of the contents of this Arrays. 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.

// Java program to demonstrate 
// Arrays.toString() method 
  
import java.util.Arrays; 
  
public class Main { 
    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)); 
    } 
} 

Output:

Integer Array: [10, 20, 15, 22, 35]

This article is contributed by Rishabh Mahrsee. If you like GeeksforGeeks and would like to contribute, you can also write an article and mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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