"Java heap space" error?

Question about the task

R or L

Java Syntax, Level 7, Lesson 9

Resolved

Why do I get a "java heap space" error, and how do I fix it?

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("rose"); // 0 list.add("love"); // 1 list.add("lyre"); // 2 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")) { list.remove(i); } if(list.get(i).contains("l") && !list.get(i).contains("r")) { list.add(i + 1, list.get(i)); } } return list; } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

16 June 2021, 02:18

Your error is caused by the program taking up too much memory. This is because you have created an infinite loop whenever something is added. The way that a for loop works is that, inside the parentheses, you have 3 sections of statements in between the semi colons. -The first section is a pre-process that accepts a line of code that gets executed before the loop starts. This is typically used to create a counter (but doesn't need to be), such as your code does with "int i = 0". -The second section is for a boolean condition that is checked at the start of each loop cycle. When true the code inside the loop block will execute, when false the loop stops. If this section is left blank then it will default to always being true. -The third also accepts a line of code. It executes this code at the end of each loop cycle. Here are some valid 'for' loops implemented that all print the numbers 0-9:

for(int i = 0; i < 10; i++){
   System.out.println(i);
}

for(int i = 0; i < 10; ){
   System.out.println(i++);
}

for(int i = 0; i < 10; System.out.println(i++));

int i = 0;
for(; i < 10; i++){
   System.out.println(i);
}

int i = 0;
for( ; ; ){
   if(i == 10) break;
   System.out.println(i++);
}

Now, back to your loop. What happens is that when an item is added it is added to the very next index, i + 1, which increases the size of the list but because you are not adjusting the value of 'i' when this occurs the very next loop cycle is going to be i + 1, which is the value you just added. Because it was a value that itself is going to pass the test to be added, it will be added again at i + 1. The loop counter increases and now test that value, which will be added again... until eventually all available memory is taken up.