Java Exceptions

An exception is an error that happens while the program runs. Catch it with try / catch so the program can carry on. finally always runs.

ExampleJava

public class Main {
  static int divide(int a, int b) {
    if (b == 0) throw new IllegalArgumentException("Cannot divide by zero");
    return a / b;
  }

  public static void main(String[] args) {
    try {
      int[] nums = {1, 2, 3};
      System.out.println(nums[5]);
    } catch (ArrayIndexOutOfBoundsException e) {
      System.out.println("Caught: " + e.getMessage());
    } finally {
      System.out.println("finally always runs");
    }

    try {
      System.out.println(divide(10, 0));
    } catch (IllegalArgumentException e) {
      System.out.println("Error: " + e.getMessage());
    }
  }
}

Output

Caught: Index 5 out of bounds for length 3
finally always runs
Error: Cannot divide by zero

Quick check

Which block always runs, error or not?

catchfinallytry

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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