try-catch-finally

14.1.1 What is an Exception?

In Java, an exception is an unexpected event that interrupts the normal flow of your program.
Examples:

• Dividing by zero.

• Accessing an invalid array index.

• Trying to open a file that doesn’t exist.

If you don’t handle exceptions properly, your program crashes.

Java uses a built-in exception handling system that lets you:

• Detect problems.

• Catch them.

• Handle them gracefully without killing the whole program.

14.1.2 Using try-catch

To handle exceptions, you wrap risky code in a try block.
If something goes wrong, Java jumps to the catch block.

Example:

java
public class TryCatchExample {
    public static void main(String[] args) {
        try {
            int result = 10 / 0; // This will cause an exception
            System.out.println("Result: " + result);
        } catch (ArithmeticException e) {
            System.out.println("Error: Cannot divide by zero.");
        }
    }
}

How this works:

• try contains code that might fail.

• If 10 / 0 happens, an ArithmeticException is thrown.

• The catch block catches it and prints a safe message.

14.1.3 Adding finally

Sometimes, you need code that always runs, whether an exception happens or not.
This is what finally is for — it runs no matter what.

Example:

java
public class TryCatchFinallyExample {
    public static void main(String[] args) {
        try {
            int[] nums = {1, 2, 3};
            System.out.println(nums[5]); // ArrayIndexOutOfBounds
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Invalid index!");
        } finally {
            System.out.println("This runs no matter what.");
        }
    }
}

Key points:

• If the try works: the finally runs.

• If the catch runs: the finally still runs.

• Good for closing files, releasing resources, or logging.