Move All the Zeros to the End of Array in Java

In Java, Array is an object. It is a non-primitive data type which stores values of similar data type.

As per the problem statement we have to move all the zeros to the end of array i.e. if an array contains n number of zeros in it then all the n number of zeros will be pushed back in an array.

Let’s explore the article to see how it can be done by using Java programming language.

To Show you Some Instances

Instance-1

Suppose the original array is {128, 0, 99, 67, 50, 0, 29, 7, 0}

After moving all the zeros to the end of array the result will be:

Elements of array after moving all the zeros to the end of array:

128 99 67 50 29 7 0 0 0

Instance-2

Suppose the original array is {23, 9, 6, 4, 0, 0, 21, 7, 0, 6, 0, 9}

After moving all the zeros to the end of array the result will be:

Elements of array after moving all the zeros to the end of array:

23 9 6 4 21 7 6 9 0 0 0 0

Instance-3

Suppose the original array is {3, 9, 5, 1, 0, 0, 11, 6, 0, 9}

After moving all the zeros to the end of array the result will be:

Elements of array after moving all the zeros to the end of array:

3 9 5 1 11 6 9 0 0 0

Algorithm

Algorithm-1 (By Using Sorting)

• Step 1 − Declare and initialize an integer array.

• Step 2 − Implement the logic for multiple approaches.

• Step 3 − Sort the array in descending order and hence zeros will get at the last position.

• Step 4 − Print the elements of the array.

Algorithm-2 (By Manual Iteration and Replacement)

• Step 1 − Declare and initialize an integer array.

• Step 2 − Implement the logic for multiple approaches.

• Step 3 − Push all non-zero elements in the left side of an array with the zero element remaining in the end.

• Step 4 − Print the elements of the array.

Syntax

To get the length of an array (number of elements in that array), there is an inbuilt property of array i.e length

Below refers to the syntax of it −

array.length

where, ‘array’ refers to the array reference.

Multiple Approaches

We have provided the solution in different approaches.

• By Using Sorting

• By Manual Iteration and Replacement

Let’s see the program along with its output one by one.

Approach-1: By Using Sorting

In this approach, array elements will be initialized in the program. Then as per the algorithm sort the array in descending order and hence zeros will get at the last position.

Example

import java.util.*;
public class Main {
   public static void main(String[] args){
      
      //Declare and initialize the array elements
      int array[] = {128, 0, 99, 67, 50, 0, 29, 7, 0};
      
      //getting length of an array
      int n = array.length;
      
      //calling user defined function
      func(array, n);
   }
   
   //user defined method
   public static void func(int array[], int n) {
   
      //sorting the array elements
      Arrays.sort(array);
      System.out.println("Elements of array after moving all the zeros to the end of array: ");
      
      //prints array using the for loop
      for (int i = n-1; i >= 0; i--) {
         System.out.print(array[i] + " ");
      }
   }
}

Output

Elements of array after moving all the zeros to the end of array: 
128 99 67 50 29 7 0 0 0 

Approach-2: By Manual Iteration and Replacement

In this approach, array elements will be initialized in the program. Then as per algorithm push all non-zero elements in the left side of an array with the zero-element remaining in the end.

Example

import java.io.*;
public class Main {
   public static void main (String[] args){
       
      //Declare and initialize the array elements
      int arr[] = {3, 9, 5, 1, 0, 0, 11, 6, 0, 9};
      
      //getting length of an array
      int n = arr.length;
      
      //calling user defined method
      func(arr, n);
   }
   
   //user defined method
   static void func(int arr[], int n) {
      // Count of non-zero elements
      int count = 0;
      
      //shifting non zero element to the left of the loop
      for (int i = 0; i < n; i++)
      if (arr[i] != 0)
      arr[count++] = arr[i];
      
      //adding the zeros to the end
      while (count < n)
      arr[count++] = 0;
      
      //printing the result
      System.out.println("Elements of array after moving all the zeros to the end of array: ");
      for (int i = 0; i < n; i++)
      System.out.print(arr[i] + " ");
   }
}

Output

Elements of array after moving all the zeros to the end of array: 
3 9 5 1 11 6 9 0 0 0

In this article, we explored how to move all the zeros to the end of array by using Java programming language.