Java.Core.Is the finally block always executed?

✅ Yes, in most cases, the finally block always executes, regardless of whether an exception occurs or not.
🚨 However, there are a few rare cases where it does NOT execute.

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1. finally Always Executes (Normal & Exception Cases)

✅ Case 1: No Exception Occurs

public class FinallyExample {
    public static void main(String[] args) {
        try {
            System.out.println("Inside try block");
        } finally {
            System.out.println("Finally block executed");
        }
    }
}

Output:

Inside try block
Finally block executed

🔹 Key Takeaway: finally always runs, even if there’s no exception.

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✅ Case 2: Exception Occurs & Is Caught

public class FinallyWithCatch {
    public static void main(String[] args) {
        try {
            int result = 10 / 0; // Throws ArithmeticException
        } catch (ArithmeticException e) {
            System.out.println("Exception caught");
        } finally {
            System.out.println("Finally block executed");
        }
    }
}

Output:

Exception caught
Finally block executed

🔹 Key Takeaway: finally executes after the catch block.

✅ Case 3: Exception Occurs & Is Not Caught

public class FinallyWithoutCatch {
    public static void main(String[] args) {
        try {
            int result = 10 / 0; // Throws ArithmeticException
        } finally {
            System.out.println("Finally block executed");
        }
    }
}

output

Finally block executed
Exception in thread "main" java.lang.ArithmeticException: / by zero

🔹 Key Takeaway: finally executes before the program crashes.

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2. When Does finally NOT Execute?

🚨 In rare cases, the finally block does NOT execute:

❌ Case 1: System.exit(0) Before finally

public class FinallyNotExecuted {
    public static void main(String[] args) {
        try {
            System.exit(0); // JVM exits immediately
        } finally {
            System.out.println("Finally block executed"); // ❌ Does NOT execute
        }
    }
}

Output:

(No output, program terminates)

❌ Case 2: JVM Crashes (OutOfMemoryError, StackOverflowError)

public class FinallyJVMCrash {
    public static void recursiveMethod() {
        recursiveMethod(); // Infinite recursion causes StackOverflowError
    }

    public static void main(String[] args) {
        try {
            recursiveMethod();
        } finally {
            System.out.println("Finally block executed"); // ❌ Does NOT execute
        }
    }
}

🔹 Key Takeaway: If the JVM crashes, finally does not run.

❌ Case 3: finally Inside a Daemon Thread That Terminates

public class FinallyDaemonThread {
    public static void main(String[] args) {
        Thread daemonThread = new Thread(() -> {
            try {
                System.out.println("Daemon thread running");
            } finally {
                System.out.println("Finally block in daemon thread"); // ❌ May NOT execute if JVM exits
            }
        });

        daemonThread.setDaemon(true);
        daemonThread.start();

        System.out.println("Main thread exits");
    }
}

🔹 Key Takeaway: If the JVM exits before the daemon thread finishes, the finally block may not execute.

3. finally vs. try-with-resources

Since Java 7, try-with-resources is a better alternative to finally for handling resources.

✅ Example: try-with-resources Automatically Closes Resources

import java.io.*;

public class TryWithResourcesExample {
    public static void main(String[] args) {
        try (FileReader file = new FileReader("test.txt");
             BufferedReader br = new BufferedReader(file)) {
            System.out.println(br.readLine());
        } catch (IOException e) {
            System.out.println("IOException occurred: " + e.getMessage());
        }
    }
}

🔹 Why is try-with-resources better?
✔ Cleaner code (no need for finally).
✔ Resources automatically close, even if an exception occurs.

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4. Summary

Scenario	Does finally Execute?
Normal execution (no exception)	✅ Yes
Exception occurs & is caught	✅ Yes
Exception occurs & is NOT caught	✅ Yes (before crash)
Inside System.exit(0)	❌ No
JVM crashes (OutOfMemoryError, StackOverflowError)	❌ No
Daemon thread terminates before execution	❌ No (if JVM exits first)

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Final Thoughts

✔ In most cases, finally always executes, whether an exception occurs or not.
✔ It does NOT execute if System.exit(0), JVM crashes, or daemon threads stop early.
✔ Use try-with-resources for resource management instead of finally.