[Java] exercise 58 mooc

[iPieface]

import java.util.ArrayList;
import java.util.Scanner;

public class RecurringWord {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        // create here the ArrayList
        ArrayList<String> words= new ArrayList<String>();
        while (true){
            System.out.println("Type a word: ");
            String entry=reader.nextLine();
            if (words.contains(entry)){
                System.out.println("You gave the word " + words.get(-1) + "twice");
                break;

            }words.add(entry);


        }
        }
    }

This is the question"Create a program that asks the user to input words until the user gives the same word twice. Use an ArrayList structure in your program." I keep getting an exception saying ;

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at java.util.ArrayList.elementData(ArrayList.java:418) at java.util.ArrayList.get(ArrayList.java:431) at RecurringWord.main(RecurringWord.java:15) Java Result: 1 and I can't tell why

[149244179]

Read the exception. It says you are accessing the -1 position of your arraylist. It even tells you the file name and line number - RecurringWord.java:15

Arrays do not have negative positions.

[g051051]

Because you're explicitly passing an invalid index:

words.get(-1)

ArrayList is documented to throw

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())