Types of Exceptions

Types of Exceptions

💡What are Exception Types?

In Java, exceptions are categorized based on when they’re detected and how they’re handled.

There are two main types:

1. Checked Exceptions

2. Unchecked Exceptions

✔️ Checked Exceptions

These are exceptions that the compiler checks at compile-time.

If your code might throw one of these, Java forces you to either:

• Handle it using try-catch, or

• Declare it using throws

🔧 Examples of Checked Exceptions:

🔸 Example:

(*We will study about this in further modules)

import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        FileReader file = new FileReader("data.txt");  // File might not exist
        file.close();
    }
}

Exception in thread "main" java.io.FileNotFoundException: data.txt (No such file or directory)

⚠️ Unchecked Exceptions

• These occur at runtime and are not checked by the compiler.

• You’re not forced to handle them — but you should, to avoid crashes.

🔧 Examples of Unchecked Exceptions:

🔸 Example:

public class Main {
    public static void main(String[] args) {
        int[] nums = {1, 2, 3};
        System.out.println(nums[5]);  // Index out of range
    }
}

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds

🧠 Error Class (Bonus: Not an Exception)

Java also has a separate branch under Throwable called Error — these are system-level failures (like memory issues).

**These are usually not handled with try-catch.

✅ Are There Any Other Ways to Handle Errors?

Yes — in very rare or critical systems, developers might try to:

🛡️ 1. Catch them cautiously:

try {
    // risky code (like recursion)
} catch (StackOverflowError e) {
    System.out.println("Stack overflow occurred!");
}

⚠️ Use this only when you must do logging, emergency cleanup, or crash reporting.

🧼 2. Use finally for cleanup:

Even if an error occurs, the finally block still runs:

try {
    // risk of OutOfMemoryError
} finally {
    System.out.println("Cleaning up resources...");
}

🧠 3. Prevent them proactively:

• Avoid infinite recursion to prevent StackOverflowError.

• Use efficient data structures and close unused objects to avoid OutOfMemoryError.

• Tune JVM memory limits (using Xmx flags) in large applications.

🧾 Recap Table