Filling Arrays from user input

Question

I'm trying to make java program that user can fill arrays with numbers then he can hunt them by typing its value the problem is when I try to fill array it only fills with last one typed. Can someone help me figure it out ?

package methods;


import java.util.Arrays;
import java.util.stream.IntStream;

public class HuntTheNumbers {

    public void huntingNumbersInArray(int[] ints, int userNumbersInput) {

        boolean contains = IntStream.of(ints).anyMatch(x->x==userNumbersInput);

        if (contains) {
            System.out.println(userNumbersInput+" is found");
        }else {
            System.out.println("value not found");
        }

    }
public void fillArray(int[] ints, int userNumbersToFillArray){

    Arrays.fill(ints, userNumbersToFillArray);
}
}

    import methods.CombineNumbers;
    import methods.HuntTheNumbers;
    
    import java.util.Arrays;
    import java.util.Scanner;
    
    public class Main {
        public static void main(String[] args) {
            HuntTheNumbers huntTheNumbers = new HuntTheNumbers();
            boolean start = true;
            int[] ints = new int[6];
            int[] firstArrayToMerge = new int[4];
            int[] secondArrayToMerge = new int[4];
            Scanner scanner = new Scanner(System.in);
            while (start) {
    
                System.out.println("======Menu======");
                System.out.println("1:Hunt the numbers");
                System.out.println("2:Combine the numbers");
                System.out.println("3:Quit");
    
                String command = scanner.next();
                if (command.equalsIgnoreCase("1")) {
                    System.out.println("Enter total number of elements");
                    int userNumberLengthInput = scanner.nextInt();
                    if (userNumberLengthInput > ints.length) {
                        start = false;
                        System.out.println("You can't put that many numbers in this array max size is 5");
                    } else {
    
                        System.out.println("Enter " + userNumberLengthInput + " elements");
                        for (int i = 0; i < userNumberLengthInput; i++) {
    
                            int userNumbersToFillArray = scanner.nextInt();
                            Arrays.fill(ints, userNumbersToFillArray);
    
                        }
    
    
                        System.out.println("Enter request value");
    
                        int requestValue = scanner.nextInt();
                        huntTheNumbers.huntingNumbersInArray(ints, requestValue);
                    }
                } else if (command.equalsIgnoreCase("2")) {
                    System.out.println("Enter total elements in first array");
                    int totalElementsInFirstArray = scanner.nextInt();
                    if (totalElementsInFirstArray > firstArrayToMerge.length) {
                        System.out.println("You can't put that many elements max size is 9");
                        start=false;
                    } else {
                        System.out.println("Enter elements of first Array");
                        for (int i = 0; i < totalElementsInFirstArray; i++) {
    
                            int userNumbersToFillArray = scanner.nextInt();
                            huntTheNumbers.fillArray(firstArrayToMerge, userNumbersToFillArray);
                        }
                    }
                    System.out.println("Enter total elements in second array");
                    int totalElementsInSecondArray = scanner.nextInt();
                    if (totalElementsInSecondArray > secondArrayToMerge.length) {
                        System.out.println("You can't put that many elements max size is 9");
                        start=false;
                    } else {
                        System.out.println("Enter elements of second Array");
                        for (int i = 0; i < totalElementsInSecondArray; i++) {
    
                            int userNumbersToFillArray = scanner.nextInt();
                            huntTheNumbers.fillArray(secondArrayToMerge, userNumbersToFillArray);
                        }
    
                    }
    
                    CombineNumbers combineNumbers = new CombineNumbers();
                    combineNumbers.mergeArrays(firstArrayToMerge, secondArrayToMerge);
                } else if (command.equalsIgnoreCase("3")) {
    
                    start=false;
                }
            }
        }
    }

with fill you fill your array with one value. So you would insert different values? — Aalexander, Jan 07 '21 at 21:43

Aalexander · Accepted Answer · 2021-01-10T09:56:33.817

Problem

The Arrays.fill() function fills your array entirely up with the same value which you pass as second argument. In your case the value of userNumbersToFillArray

Here an Example:

public static void main(String[] args) 
    { 
        int ar[] = {2, 2, 1, 8, 3, 2, 2, 4, 2}; 
  
        // To fill complete array with a particular 
        // value 
        Arrays.fill(ar, 10); 
        System.out.println("Array completely filled" + 
                  " with 10\n" + Arrays.toString(ar)); 
    } 
}

Outputs:

Array completely filled with 10
[10, 10, 10, 10, 10, 10, 10, 10, 10]

Solution

To solve this you can simply assign inside your loop the user-input value to an array element by its indice.

Write instead of

 Arrays.fill(ints, userNumbersToFillArray);

This here

ints[i] = userNumbersToFillArray;

Here you can read more about Arrays.fill()

https://www.geeksforgeeks.org/arrays-fill-java-examples/

Jan · Answer 2 · 2021-01-07T21:56:04.063

According to the docu Arrays.fill()

"Assigns the specified int value to each element of the specified array of ints."

So you are filling and array with e.g 5s ([5,5,5,5]).

And after the next Input you are doing the exact same with another number ({4,4,4,4}), hence why you end up with an array full of the last input.

Instead try writing every index of the array serparately like this:

public static void main(String[] args) {
    int[] ints = new int[5];
    Scanner scanner = new Scanner(System.in);

    //Foreach index of the array ask the user for a number.
    // And then change that index to the input
    for(int index= 0; index < ints.length; index++){
        System.out.println("Add a new number: ");
        int newInt = scanner.nextInt();
        ints[index] = newInt;
    }
    //Just print all values
    System.out.println(Arrays.toString(ints));
}

Filling Arrays from user input

2 Answers2

Problem

Solution