Making arrays by reading user input

[apfroggy0408]

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.

[Zeroshade15]

mmm yes .. i see..

[danielstoner]

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]);
        }
    }
}

[apfroggy0408]

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...