Console program in Java to concatenate two integer arrays created by the user.

ArrayConcatenation.java

import java.util.Scanner;
import java.util.Arrays;

public class ArrayConcatenation {

    static Scanner sc = new Scanner(System.in);
    static int[] arrayOne;
    static int[] arrayTwo;
    static int[] finalArray;

    public static void main(String args[]) {

        int arrayOneSize;
        String arrayOneIdentifier = "first";

        int arrayTwoSize;
        String arrayTwoIdentifier = "second";

        System.out.println("\nWelcome to the program to concatenate two arrays of integer numbers.");


        arrayOneSize = requestArraySize(arrayOneIdentifier);

        arrayOne = new int[arrayOneSize];

        fillArray(arrayOne, arrayOneIdentifier);


        arrayTwoSize = requestArraySize(arrayTwoIdentifier);

        arrayTwo = new int[arrayTwoSize];

        fillArray(arrayTwo, arrayTwoIdentifier);


        concatenate(arrayOne, arrayTwo);

    }

    /**
     * This method requests the user to determine the size of an array
     *
     * @param pArrayIdentifier String used to let the user know which array size is going to determine
     * @return Returns the size of the array determined by the user.
     */
    private static int requestArraySize(String pArrayIdentifier) {

        boolean validSize = false;
        int numberToReturn = 0;
        String error = "\nError. The size must be an integer number greater than 0.";

        while (!validSize) {
            System.out.println("\nPlease insert the size of the " + pArrayIdentifier + " array:");
            if (sc.hasNextInt()) {
                numberToReturn = sc.nextInt();
                if (numberToReturn > 0) {
                    validSize = true;
                } else {
                    // The user entered an integer number less than or equal to 0
                    System.out.println(error);
                }
            } else {
                // The user did not enter an integer number
                System.out.println(error);
            }
            sc.nextLine();
        }

        return numberToReturn;
    }

    /**
     * This method fills each position of the array with the number specified by the user
     *
     * @param pArray           The array to fill
     * @param pArrayIdentifier The String to let the user know which array is working with
     */
    private static void fillArray(int[] pArray, String pArrayIdentifier) {

        boolean validInteger = false;

        for (int i = 0; i < pArray.length; i++) {
            System.out.println("\nPlease insert the value for position " + i + " of the " + pArrayIdentifier + " array:");
            while (!validInteger) {
                if (sc.hasNextInt()) {
                    pArray[i] = sc.nextInt();
                    validInteger = true;
                } else {
                    System.out.println("Error. Not a valid integer number.");
                }
                sc.nextLine();
            }
            validInteger = false;
        }
        System.out.println("\nThe " + pArrayIdentifier + " array elements are: " + Arrays.toString(pArray));
    }

    /**
     * This method concatenates the arrays previously created by the user.
     *
     * @param pArrayOne The first array to concatenate.
     * @param pArrayTwo The second array to concatenate.
     */
    private static void concatenate(int[] pArrayOne, int[] pArrayTwo) {

        int arrayOneLength = pArrayOne.length;

        int arrayTwoLength = pArrayTwo.length;

        // This variable keeps track of the index already filled with a number
        int counter = 0;

        finalArray = new int[arrayOneLength + arrayTwoLength];

        for (int i = 0; i < arrayOneLength; i++) {
            finalArray[i] = pArrayOne[i];
            counter = i;
        }

        // One is added to the counter, so we can start filling the next available index at the array
        counter++;

        for (int i = 0; i < arrayTwoLength; i++) {
            finalArray[counter] = pArrayTwo[i];
            counter++;
        }

        System.out.println("\nThe final array is: " + Arrays.toString(finalArray));
    }

}