绘制分形时出现Index out of bounds异常求助

Hey there, let's figure out why you're hitting that index out of bounds error on lines 41 and 50—especially since calling takken.get(0).draw(g2d) works fine, but any index above 0 breaks things. Here are the most likely culprits and steps to fix them:

1. Your takken collection is smaller than you think #

The biggest red flag here is that only index 0 works. That means your collection probably only has one element in it, even though you expected more. To confirm this:

• Add a debug print right before the lines that throw errors:

  System.out.println("Total elements in takken: " + takken.size());
  

  If the output is 1, you know the issue is that your code isn't adding enough elements to takken.

2. Check how you're adding elements to takken #

Double-check all places where you call takken.add(...):

• Did you accidentally put the add call inside a conditional that only runs once? (Like a recursive fractal generation loop where the base case triggers too early, stopping new branches from being added.)
• Is there a bug in your fractal logic that prevents new segments from being created and added to the collection? For example, maybe you're not calculating the next fractal segment's coordinates correctly, so the code skips adding new elements.

3. Fix your index access logic #

If your takken collection does have multiple elements, the problem is likely how you're accessing those indices:

• Loop boundary mistake: If you're using a for loop, you might have written i <= takken.size() instead of i < takken.size(). Remember, Java collections are 0-indexed—so the last valid index is takken.size() - 1.
  Example of wrong code:

  // This will fail when i equals takken.size()
  for (int i = 0; i <= takken.size(); i++) {
      takken.get(i).draw(g2d);
  }
  

  Fixed code:

  for (int i = 0; i < takken.size(); i++) {
      takken.get(i).draw(g2d);
  }
  

• Hardcoded indices: If you're manually using indices like takken.get(1) or takken.get(2), make sure those positions actually exist. Instead of hardcoding, use an enhanced for loop to avoid index issues entirely:

  for (Tak tak : takken) {
      tak.draw(g2d);
  }
  

4. Rule out concurrent modification (less likely, but possible) #

If you're modifying takken (like removing elements) while trying to access it (especially in Swing's event threads), this could cause the size to change unexpectedly. Make sure all modifications to takken happen before you start drawing, or use a thread-safe collection if needed.

If you can share the specific code from lines 41, 50, and the parts where you initialize and add elements to takken, we can narrow this down even further!

内容的提问来源于stack exchange，提问作者Siebe Hiel