Java ArithmeticException异常求助：出现除以零错误

Hey there! Let's work through fixing that division-by-zero error you're hitting in your draw() method.

First, let's break down what the error log is telling us clearly:

Exception in thread "Thread-2" java.lang.ArithmeticException: / by zero. at MyPackage.MyClass.draw (MyClass.java:180)

This means on line 180 of your MyClass.java file, there’s a division operation using either col or row (or both) as the denominator—and right now both values are 0. Java throws this exception because dividing by zero is mathematically undefined, so the program can’t proceed safely.

Here’s a step-by-step plan to diagnose and fix this:

• First, pinpoint the exact division on line 180
  Open up MyClass.java and jump straight to line 180. You’ll probably see code like int cellSize = canvasWidth / col; or double aspectRatio = totalHeight / row;—that’s the line triggering the crash.

• Trace where col and row are getting their values
  Ask yourself: Are these variables passed into the draw() method as parameters? Are they initialized elsewhere in the class? Did a prior calculation fail to generate a valid positive number (like if you’re calculating rows from empty user input that defaults to 0)? Tracking their origin will help you fix the root cause, not just the symptom.

• Add defensive checks before the division
  A quick fix to prevent crashes is to validate that col and row are positive integers before doing any division. For example:

  // Inside your draw() method, right before line 180
  if (col <= 0 || row <= 0) {
      // Log the issue for debugging
      System.err.println("Invalid values detected: col=" + col + ", row=" + row);
      // Set safe default values to keep the program running
      col = col <= 0 ? 1 : col;
      row = row <= 0 ? 1 : row;
  }
  // Now proceed with your division safely
  int tileWidth = canvasWidth / col;
  

• Fix the root cause of the 0 values
  Defensive checks stop crashes, but you should also address why col and row are 0:

  • If they come from user input, add validation to ensure the user enters a number greater than 0.
  • If they’re calculated from other data, check that the source data isn’t empty or zero (like if you’re dividing a total size by a tile size that was never set).

If you’re still stuck, sharing a few lines of code around line 180 (and how col/row are defined or set) will help narrow down the exact issue even faster.

内容的提问来源于stack exchange，提问作者Francesco Mesiano