Remove/Delete An Element From An Array In Java

Learn Various Methods to Delete or Remove an element from an Array in Java such as Using another array, Using Java 8 Streams, Using ArrayList:

Java arrays do not provide a direct remove method to remove an element. In fact, we have already discussed that arrays in Java are static so the size of the arrays cannot change once they are instantiated. Thus we cannot delete an element and reduce the array size.

So if we want to delete or remove an element from the array, we need to employ different methods that are usually workarounds.

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Remove/Delete An Element From An Array In Java

In this tutorial, we will discuss the various methods to delete an element from an array.

It includes:

• Using another Array
• Using Java 8 streams
• Using ArrayList
• Using System.arraycopy()

Using Another Array

This is the traditional and somewhat inefficient method of deleting an array element. Here we define a new array with size less than 1 to the original array. Then we copy the elements from the original array to the new array. But while doing this copying, we skip the element at the specified index.

This way we copy all the elements except the element to be deleted to the new array indicating that the element is deleted.

We can represent this operation pictorially as shown below.

Let’s implement this method in a Java program.

import java.util.Arrays; 
class Main {   
public static void main(String[] args) 
    {   
        // define original array 
        int[] tensArray = { 10,20,30,40,50,60}; 

        // Print the original array 
        System.out.println("Original Array: " + Arrays.toString(tensArray)); 

        // the index at which the element in the array is to be removed 
        int rm_index = 2; 

        // display index 
        System.out.println("Element to be removed at index: " + rm_index); 

        // if array is empty or index is out of bounds, removal is not possible 
          if (tensArray == null
            || rm_index< 0
            || rm_index>= tensArray.length) { 

            System.out.println("No removal operation can be performed!!");
        } 
        // Create a proxy array of size one less than original array
        int[] proxyArray = new int[tensArray.length - 1]; 

        // copy all the elements in the original to proxy array except the one at index 
        for (int i = 0, k = 0; i <tensArray.length; i++) { 

            // check if index is crossed, continue without copying 
            if (i == rm_index) { 
                continue; 
            } 

            // else copy the element
            proxyArray[k++] = tensArray[i]; 
        } 

       // Print the copied proxy array 
       System.out.println("Array after removal operation: " + Arrays.toString(proxyArray)); 
    } 
}

Output:

Using Java 8 Streams

Streams are a new addition to Java from version 8 onwards. Using Java8 streams, we can delete an element from an array. In order to do this, first, the array is converted to a stream. Then the element at the specified index is deleted using the filter method of streams.

Once the element is deleted, using the ‘map’ and ‘toArray’ methods, the stream is converted back to the array.

The implementation of removing an element from an array using stream is shown below.

import java.util.Arrays; 
import java.util.stream.IntStream; 
  class Main {   
    // Function to remove the element 
    public static int[] removeArrayElement(int[] oddArray,  
                      int index) 
    { 
         //array is empty or index is beyond array bounds
         if (oddArray == null || index < 0 || index >= oddArray.length) { 

              return oddArray; 
        } 
          // delete the element at specified index and return the array 
          return IntStream.range(0, oddArray.length) .filter(i -> i != index) 
            .map(i ->oddArray[i]).toArray(); 
    } 

    public static void main(String[] args)  {   
         int[] oddArray = { 1, 3,5,7,9,11};     // define array of odd numbers 

       System.out.println("Original Array: " + Arrays.toString(oddArray));   // Print the resultant array 
       int index = 2; 	// index at which element is to be removed
       System.out.println("Element to be removed at index: " + index); 	// display index

        // function call removeArrayElement
        oddArray = removeArrayElement(oddArray, index); 

        // Print the resultant array 
        System.out.println("Array after deleting element: "  + Arrays.toString(oddArray)); 
    } 
}

Output:

Using ArrayList

We can use an ArrayList to perform this operation. To remove an element from an array, we first convert the array to an ArrayList and then use the ‘remove’ method of ArrayList to remove the element at a particular index.

Once removed, we convert the ArrayList back to the array.

The following implementation shows removing the element from an array using ArrayList.

import java.util.*;
import java.util.stream.*;

class Main {   
     public static int[] remove_Element(int[] myArray,  int index) 
    { 
	if (myArray == null || index < 0 || index >= myArray.length) { 
	    System.out.println("non-existing index");
	    return myArray; 
	} 
	//array to arrayList
	List<Integer>arrayList = IntStream.of(myArray) .boxed().collect(Collectors.toList()); 
	// Remove the specified element 
	arrayList.remove(index); 

	// return the resultant array 
	returnarrayList.stream().mapToInt(Integer::intValue).toArray(); 
    } 
    public static void main(String[] args)  { 
       int[] myArray = { 11,22,33,44,55,66,77,88,99,111 }; 
       System.out.println("Original Array: " + Arrays.toString(myArray)); 
       int index = 10; 
       System.out.println("Index at which element is to be deleted: " + index); 
       myArray = remove_Element(myArray, index); 
       System.out.println("Resultant Array: " + Arrays.toString(myArray) + "\n"); 

      index = 2; 
      System.out.println("Index at which element is to be deleted: " + index); 
      myArray = remove_Element(myArray, index); 
      System.out.println("Resultant Array: " + Arrays.toString(myArray)); 
    } 
}

Output:

The above program produces output for two conditions. First, a non-existing index (10) is passed i.e. beyond the current array size. The program displays an appropriate message and does not delete any element.

In the second case, an index = 2 is passed. This time the element at position 2 is deleted and the resultant array is passed.

Using System.arraycopy ()

This method is similar to the first method except that we use the ‘arrayCopy’ method for copying the elements of the original array into the new array.

First, we copy the elements of the original array from 0 to index into the new array. Next, we copy the elements from index+1 until length into the new array. Thus while copying, we skip the element at the specified index and generate a new array.

This new array indicates the resultant array that is obtained after deleting an element at the specified index.

import java.util.Arrays; 

class Main { 

    public static void main(String[] args) 
    { 
        // define the array of integers
        int[] intArray = { 10,20,30,40,50 }; 

        // display the original array 
        System.out.println("Original Array: "
                           + Arrays.toString(intArray)); 

        // index at which the element is to be deleted 
        int index = 2; 

        // the index 
        System.out.println("Element to be deleted at index: "
                           + index); 

        // check if the array is empty or index is out of bounds 
        if (intArray == null || index < 0  || index >= intArray.length) { 
            System.out.println("No removal operation can be performed!!");
        } 

        // create an array to hold elements after deletion
       int[] copyArray = new int[intArray.length - 1]; 

        // copy elements from original array from beginning till index into copyArray
        System.arraycopy(intArray, 0, copyArray, 0, index); 

        // copy elements from original array from index+1 till end into copyArray
        System.arraycopy(intArray, index + 1, copyArray, index, intArray.length - index - 1); 

        // display the copied array after deletion 
        System.out.println("Array after deleting an element: "
                           + Arrays.toString(copyArray)); 
    } 
}

Output:

Frequently Asked Questions

Q #1) How to remove one element from an Array?

Answer: Java does not provide a direct method to remove an element from the array. But given an index at which the element is to be deleted, we can use ArrayList to remove the element at the specified index.

For this, first, we convert the array to ArrayList and using the remove method we remove the element. Once that is done, we convert the ArrayList back to the array. There are also several other workarounds that we can employ for this purpose.

Q #2) What does ArrayList remove do?

Answer: ArrayList remove method removes the element in the ArrayList at a given index that is provided as an argument.

Q #3) How do you remove Duplicates from an Array in Java?

Answer: Duplicate elements from an array can be removed by using a temporary array that will count the elements one by one and only put the unique elements in the temporary array. An array needs to be sorted to remove the duplicates.

Q #4) Does Filter return a new array?

Answer: Yes. Filter returns the new array without affecting the original array.

Q #5) How does Remove work in Java?

Answer: The remove method of ArrayList in Java removes the element at the specified index. In the linked list as well the remove method removes the node at the given position.

Conclusion

In this tutorial, we have seen the various way or workarounds using which we can remove the element from an array at a given index.

In our subsequent topics, we will discuss some more operations performed on arrays in Java.

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