Making arrays by reading user input

Code:

---

ArrayList<String> mm = new ArrayList<String>();
                Scanner input = new Scanner(System.in);
       
                        System.out.println("Enter the string: ");
                String str = input.nextLine().trim();
       
                System.out.println("Enter an index: ");
                int index = input.nextInt();
       
                mm[index] = str;  <---
                System.out.println(mm);
                System.out.println(index);
               
                for (int k = 0; k < size; k++)
                        System.out.println(mm[k]); <--

---

Why won't this work?

array required, but java.util.ArrayList<java.lang.String> found
array required, but java.util.ArrayList<java.lang.String> found

errors occur at arrows.

mmm yes .. i see..

Because mm is an ArrayList not an array :). This means you cannot use the mm[idx] syntax. Arrays are special objects in Java. On the other hand the ArrayList is just a list object backed by an array :)
Use this code to compare the two concepts:

Code:

---

public class ArrayTest
{
    public static void main(String[] args)
    {
        useArray();
        useList();
    }

    private static void useList()
    {
        ArrayList<String> mm = new ArrayList<String>();
        Scanner input = new Scanner(System.in);

        System.out.println("Enter the string: ");
        String str = input.nextLine().trim();

        mm.add(str);
        System.out.println(mm);

        for (int k = 0; k < mm.size(); k++)
        {
            System.out.println("mm(" + k + ") = " + mm.get(k));
        }
    }

    private static void useArray()
    {
        String[] mm = new String[10];

        Scanner input = new Scanner(System.in);

        System.out.println("Enter the string: ");
        String str = input.nextLine().trim();

        System.out.println("Enter an index: ");
        int index = input.nextInt();

        if (index < mm.length)
        {
            mm[index] = str;
        }

        for (int k = 0; k < mm.length; k++)
        {
            System.out.println("mm[" + k + "] = " + mm[k]);
        }
    }
}

---

So I've decided to abandon the array ship, and just use the different String methods.

Here's what I have.

Code:

---

import java.util.*;
public class p499proj12l2 {

    public static void main(String args[])
    {
           
            Scanner input = new Scanner(System.in);
            System.out.println("Please enter word: ");
            String sent = input.nextLine();
            String trimsent = sent.trim();
            int length = trimsent.length();
            int gate;
            int index;
            do{
                    System.out.println("Enter index wanted: ");
                    index = input.nextInt();
            int        b = length - 1;
                    if (index > b)
            {
                    System.out.println("Index doesn't exist");
                    gate = 0;
            }
            else
            {
                    gate = 1;
            }
            }
            while(gate != 1);
           
            Recurse(trimsent, index, length);
           
    }
    public static String Recurse(String trimsent, int index, int length)
    {
           
            if(index <= length)
            {
                   
                   
                    Recurse(trimsent, index + 1 , length);
                    char chars = trimsent.charAt(index);
                    System.out.print(chars);
                   
            }
            else
            {
                    System.out.println();
                    System.out.println(trimsent);
            }
   
           
            return null;
    }

           
           
           
           
           
           
   
   
   
}

---

What the code is supposed to do is ask for a word and an index. At the entered index the word is supposed to be spelled backwards from that spot using a recursive method.

i.e. shoe index 1 = seoh.

I'm having trouble just with my Recurse method.

Because for some reason I get these results...

Shoe , index 1 = eohs
Shoe , index 2 = eoh
Shoe , index 3 = eo

Now I see the pattern, but I'm confused on how it's getting there.
My else statement always runs first too for some reason unbeknownst to me...