code is running forever D:

Question about the task

R or L

Java Syntax, Level 7, Lesson 9

Resolved

Having issues requuriement 2.2 See comments Thanks for the help!

1. Create a list of words and populate it yourself.
2. The fix method should:
2.1. remove all words containing the letter "r" from the list
2.2. duplicate all words containing the letter "l".
2.3. if a word contains both "r" and "l", then leave it unchanged.
2.4. don't do anything to other words.

For example:
rose lyre love

Output:
lyre love love

Requirements:

The program must not read data from the keyboard.
The fix method should remove all words containing the letter "r" from the list. There is an exception: words containing both "r" and "l" should be left alone.
The fix method must duplicate words containing the letter "l" (add another instance of this word to the list). There is an exception: words containing both "l" and "r" should not be duplicated.
The fix method should not do anything with words that contain both "l" and "r".
The fix method should not do anything with words that don't contain either "l" or "r".

package com.codegym.task.task07.task0716; import java.util.ArrayList; /* R or L */ public class Solution { public static void main(String[] args) throws Exception { ArrayList<String> list = new ArrayList<String>(); list.add("rrrrrrr"); // 0 - should delete - WORKS FINE list.add("rl"); // 1 - should keep, has r and l - WORKS FINE list.add("bob"); // 2 - should keep, all other words - WORKS FINE list.add("l"); // 3 - should make copy* - PROBLEM. list = fix(list); for (String s : list) { System.out.println(s); } } public static ArrayList<String> fix(ArrayList<String> list) { for (int i = 0; i < list.size(); i++) { if ((list.get(i).contains("r")) && (list.get(i).contains("l"))) { continue; } else if (list.get(i).contains("l")) { String wordCopy = list.get(i);//got the a copy of the word containg "l" and stored it in this var System.out.println(wordCopy); //print succesfully > the word with l list.add(wordCopy); // problem here... the could just runs forever... i just wanted one copy lol. } else if (list.get(i).contains("r")) { list.remove(i); } } return list; } }

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Usman Full Stack Developer at QA

6 July 2021, 13:25

i fixed it guys, thanks for the help. here is the final code:

package com.codegym.task.task07.task0716;

import java.util.ArrayList;

/*
R or L

*/

public class Solution {
    public static void main(String[] args) throws Exception {
        ArrayList<String> list = new ArrayList<String>();
        list.add("rose");
        list.add("lyre");
        list.add("love");

        list = fix(list);

        for (String s : list) {
            System.out.println(s);
        }
    }

    public static ArrayList<String> fix(ArrayList<String> list) {

        ArrayList<String> newList = new ArrayList<String>(); // new list approach

        for (int i = 0; i < list.size(); i++) {

            if ((list.get(i).contains("r")) && (list.get(i).contains("l"))) {
                newList.add(list.get(i));
            } else if (list.get(i).contains("l")) {
                String wordCopy = list.get(i);
                newList.add(wordCopy);
                newList.add(wordCopy);
            } else if (list.get(i).contains("r")) {
                continue;
            } else {
                newList.add(list.get(i));
            }
        }

        return newList;
    }
}

MrPreston

Level 11 , Edinburgh, United Kingdom

6 July 2021, 13:12

The problem here is you are adding values to the end of a list that you are looping over. So if you find a word containing "l" you add it to the end of the list you are currently working on. This means that the end of the list now has a word with l in it. So when you get to the end of the list, you will find that same word again, add it again and your loop will now go one more time because there is a new word now, and that new word is the word you just added with "l" in it and the process will continue forever. To fix this I suggest you make a new list in the fix method, add the words you find to the new list. Then return this new list.

Guadalupe Gagnon

Level 37 , Tampa, United States

6 July 2021, 13:10

useful

You already figured out the problem: when an item is added to the list it is added to the end of the list. This is a problem because: - it adds it to the list the algorithm is currently using - the for loop runs as long as 'i' is less than list.size(). Adding an item increases the size. - adding the item at the end of the list means that the algorithm will reach that item again, which means it will add it to the end again, which increases the size of the list, and it will reach that item again infinitely. I broke that down into 3 points because fixing any one of those 3 points will fix this code.