L_Manipulation_Basics

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.stream.Collectors;

public class ListManipulationBasics {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        List<Integer> numbers =
                Arrays.stream(scanner.nextLine().split(" "))
                        .map(Integer::parseInt)
                        .collect(Collectors.toList());
        String line = "";
        List<Integer> result = new ArrayList<>();
        while (!("end").equals(line = scanner.nextLine())) {
            String[] commandArray = line.split("\\s+");
            String command = commandArray[0];
            switch (command) {
                case "Add":
                    int numberToAdd = Integer.parseInt(commandArray[1]);
                    result = addElement(numbers, numberToAdd);
                    break;
                case "Remove":
                    int numberToRemove = Integer.parseInt(commandArray[1]);
                    result = removeElement(numbers, numberToRemove);
                    break;
                case "RemoveAt":
                    int indexToRemove = Integer.parseInt(commandArray[1]);
                    result = removeAtElement(numbers, indexToRemove);
                    break;
                case "Insert":
                    int numberToInsert = Integer.parseInt(commandArray[1]);
                    int indexToInsert = Integer.parseInt(commandArray[2]);
                    result = insertElements(numbers, numberToInsert, indexToInsert);
                    break;
            }
        }
        String output = joinElementByDelimiter(result, " ");
        System.out.println(output);
    }

    private static List<Integer> addElement(List<Integer> numbers, int numberToAdd) {
        numbers.add(numberToAdd);
        return numbers;
    }

    private static List<Integer> removeElement(List<Integer> numbers, int numberToRemove) {
        Object numToRemove;
        numToRemove = numberToRemove;
        numbers.remove(numToRemove);
        return numbers;
    }

    private static List<Integer> removeAtElement(List<Integer> numbers, int indexToRemove) {
        numbers.remove(indexToRemove);
        return numbers;
    }

    private static List<Integer> insertElements(List<Integer> numbers, int numberToInsert, int indexToInsert) {
        numbers.add(indexToInsert, numberToInsert);
        return numbers;
    }

    private static String joinElementByDelimiter(List<Integer> numbers, String delimiter) {
        String output = "";
        for (int i = 0; i < numbers.size() ; i++) {
            output = String.format("%s%s", output, new DecimalFormat("0.#").format(numbers.get(i)) + delimiter);
        }
        return output;
    }
}