I want to create an unlimited array, but there is some problem in my code that causes

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at JTB.main(JTB.java:13)

Here's my code with comments.

import java.util.Scanner;

public class JTB {
    public static void main(String args[]) {
        //variables and object(s)
        Scanner scanner = new Scanner(System.in);
        int jtb[] = {};
        int input = 0;
        int counter = 0;
        
        //Asks array input from user, 5 should be entered to cancel the loop.
        while(input != 5) {
            input = scanner.nextInt(); //line 13
            jtb[counter] = input;
              counter;
        }
        
        //prints out the array no. and the integer inside it.
        for(int counter1 = 0; counter1 < jtb.length;   counter1) {
            System.out.println("Array "   counter1   ": "   jtb[counter1]);
        }
    }
}

How do I make it work?

CodePudding user response：

Java does not support dynamic arrays. You can use ArrayList instead.

CodePudding user response：

You've defined jtb as an empty array. Any attempt to add to it will cause an ArrayIndexOutOfBoundsException.

You could give it a reasonable size instead of creating an empty array, but it will ultimately be limited. You could use a List instead.

List<Integer> jtb = new LinkedList<>();
int input = 0;

//Asks array input from user, 5 should be entered to cancel the loop.
while(input != 5) {
    input = scanner.nextInt(); //line 13
    jtb.add(input);
}

CodePudding user response：

If you want to get unlimited space use ArrayList, LinkedList etc check into java collection

Here down is ArrayList example

public static void main(String args[]) {
        Scanner scanner = new Scanner(System.in);
        ArrayList<Integer> data = new ArrayList<>();
        Integer counter = 0;
        Integer input = 0;
        while(input != 5) {
            input = scanner.nextInt();
            data.add(input);
            counter  ;
        }
        for(Integer extractData: data) {
            System.out.print("Print List:"   extractData   "\n");
        }
    }

Here down is LinkedList example

import java.util.*;
class Node {
    Node next;
    int data;

    Node(int data) {
        this.data = data;
    }
}

public class Main
{
    Node head;

    public void appendList(int data) {
        if (head == null) {
            head = new Node(data);
            return;
        }

        Node current = head;
        while (current.next != null) {
            current = current.next;
        }
        current.next = new Node(data);
    }
    
    public void printList() {
        Node current = head;
        System.out.print("{ ");
        while (current != null) {
            System.out.print(current.data   ", ");
            current = current.next;
        }
        System.out.print("\b\b }");
    }
    public static void main(String args[]) {
        Main linkedList = new Main();
        linkedList.appendList(1);
        linkedList.appendList(2);
        linkedList.appendList(3);
        linkedList.appendList(4);
        linkedList.appendList(5);
        linkedList.printList();
    }
}

CodePudding user response：

In Java there is no dynamically growing nature of array. If you want a dynamically growing type of array then you have to go with the collection api. Use ArrayList to achieve goal.

      public static void main1(String args[]) {
            //variables and object(s)
            Scanner scanner = new Scanner(System.in);
            List<Integer> jtb = new ArrayList<>();
            int input = 0;
            
            //Asks array input from user, 5 should be entered to cancel the loop.
            while(input != 5) {
                input = scanner.nextInt(); //line 13
                jtb.add(input);
            }
            
            //prints out the array no. and the integer inside it.
            for(int index = 0; index < jtb.size();   index) {
                System.out.println("Array "   index   ": "   jtb.get(index));
            }
        }

CodePudding user response：

If you can't use collection api, you could implement a simpler one, but it's not unbounded, and the maximum array length should be Integer.max_value:

        //variables and object(s)
        Scanner scanner = new Scanner(System.in);
        int currentCapacity = 10;
        int jtb[] = new int[currentCapacity];
        int size = 0;
        int input = 0;
        int counter = 0;
        //Asks array input from user, 5 should be entered to cancel the loop.
        while(input != 5) {
            input = scanner.nextInt(); //line 13
            if (currentCapacity == size) {
                // Increases the capacity, for example, double the capacity
                int newCapacity = currentCapacity * 2;
                // Todo: consider overflow
                jtb = Arrays.copyOf(jtb, newCapacity);
                currentCapacity = newCapacity;
            }
            size  ;
            jtb[counter] = input;
              counter;
        }