Java Program to Return the Elements at Odd Positions in a List

Last Updated : 23 Jul, 2024

Given a List, the task is to return the elements at Odd positions in a list. Let’s consider the following list.

Clearly, we can see that elements 20, 40, 60 are at Odd Positions as the index of the list is zero-based. Now we should return these elements.

Approach 1:

Initialize a temporary value with zero.
Now traverse through the list.
At each iteration check the temporary value if value equals to odd then return that element otherwise just continue.
After each iteration increment the temporary value by 1.
However, this can be done without using temporary value. Since the data in the list is stored using fixed index therefore we can directly check if the index is odd or even and return the element accordingly

Example:

Java

// Java Program to Return the Elements
// at Odd Positions in a List
import java.io.*;
import java.util.*;

class GFG {
  
    public static void main(String[] args)
    {
        // Creating our list from above illustration
        List<Integer> my_list = new ArrayList<Integer>();
        my_list.add(10);
        my_list.add(20);
        my_list.add(30);
        my_list.add(40);
        my_list.add(50);
        my_list.add(60);

        // creating a temp_value for checking index
        int temp_val = 0;

        // using a for-each loop to
          // iterate through the list
        System.out.print("Elements at odd position are : ");
        for (Integer numbers : my_list) {
            if (temp_val % 2 != 0) {
                System.out.print(numbers + " ");
            }
            temp_val += 1;
        }
    }
}

Output

Elements at odd position are : 20 40 60

Approach 2:

Traverse the list starting from position 1.
Now increment the position by 2 after each iteration. By doing this we always end up in an odd position.
Iteration 1: 1+2=3
Iteration 2: 2+3=5
Iteration 3: 5+2=7
And so on.
Return the value of the element during each iteration.

Example:

Java

// Java Program to Return the Elements
// at Odd Positions in a List

import java.io.*;
import java.util.*;

class GFG {
  
    public static void main(String[] args)
    {
        // creating list from above illustration
        List<Integer> my_list = new ArrayList<>();
        my_list.add(10);
        my_list.add(20);
        my_list.add(30);
        my_list.add(40);
        my_list.add(50);
        my_list.add(60);

        // iterating list from position one and incrementing
        // the index value by 2
        System.out.print(
            "Elements at odd positions are : ");
      
        for (int i = 1; i < 6; i = i + 2) {
            System.out.print(my_list.get(i) + " ");
        }
    }
}

Output

Elements at odd positions are : 20 40 60

Approach 3:

Create and initialize a list.
Create a stream of list elements from position 0 to size of the list.
Use the filter() method to keep only positions that are odd.
Retrieve the value of the filtered positions.
Collect the filtered elements into a new list.
Return the new list.

Example:

Java

// Java Program to Return the Elements
// at Odd Positions in a List
import java.util.*;
import java.util.stream.*;

public class GFG {
    public static void main(String[] args) {
        // Creating our list
        List<Integer> my_list = Arrays.asList(10, 20, 30, 40, 50, 60);
        // filtering out odd position elements
        List<Integer> oddPosList = IntStream.range(0, my_list.size())
                                   .filter(numbers -> numbers % 2 != 0)
                                   .mapToObj(my_list::get)
                                   .collect(Collectors.toList());
        // printing the filtered elements
        System.out.println("Elements at odd position are : " + oddPosList);
    }
}

Output

Elements at odd position are : [20, 40, 60]

Java Program to Rotate Elements of the List

uchiha1101

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Java Program to Return the Elements at Odd Positions in a List

Approach 1:

Example:

Approach 2:

Example:

Approach 3:

Example:

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