🔴 Advanced · Lesson 23

Exception Handling

Written and reviewed by Gagan Bhardwaj · Senior IT Faculty · 15+ years’ experience

What is Exception Handling?

An exception is an unexpected event that occurs during program execution and disrupts the normal flow — for example dividing by zero, accessing an array out of bounds, or opening a missing file. Exception handling lets your program deal with such errors gracefully instead of crashing.

The Five Keywords

Keyword	Use
`try`	Wraps the risky code.
`catch`	Handles the exception if one occurs.
`finally`	Always runs (cleanup), whether or not an exception occurred.
`throw`	Manually throws an exception.
`throws`	Declares that a method might throw an exception.

Example

Java

public class Main {
    public static void main(String[] a) {
        try {
            int x = 10 / 0;        // risky
        } catch (ArithmeticException e) {
            System.out.println("Cannot divide by zero");
        } finally {
            System.out.println("Done");   // always runs
        }
    }
}

▶ Output

Cannot divide by zero
Done

Checked vs Unchecked Exceptions

Type	Checked at	Examples
Checked	Compile time (must handle)	IOException, SQLException
Unchecked	Runtime	ArithmeticException, NullPointerException, ArrayIndexOutOfBounds

💡 Why handle exceptions?

Without handling, one error crashes the whole program. With handling, you show a friendly message and keep running — essential for real apps.

⚠️ Common mistake

Never leave an empty catch {} block — it hides bugs. At least log the error.

Summary

Exceptions disrupt normal flow; handling prevents crashes.
Keywords: try, catch, finally, throw, throws.
finally always runs; checked exceptions must be handled, unchecked occur at runtime.

Exception Handling क्या है?

Exception program चलते समय होने वाली एक अनचाही घटना है जो सामान्य flow को रोक देती है — जैसे zero से भाग देना, array की सीमा से बाहर जाना, या गायब file खोलना। Exception handling ऐसी errors को crash हुए बिना संभालने देता है।

पाँच Keywords

Keyword	उपयोग
`try`	जोखिम भरे code को लपेटता है।
`catch`	exception होने पर संभालता है।
`finally`	हमेशा चलता है (cleanup)।
`throw`	manually exception फेंकता है।
`throws`	बताता है कि method exception फेंक सकता है।

उदाहरण

Java

try {
    int x = 10 / 0;
} catch (ArithmeticException e) {
    System.out.println("Cannot divide by zero");
} finally {
    System.out.println("Done");
}

▶ Output

Cannot divide by zero
Done

Checked vs Unchecked

प्रकार	कब check	उदाहरण
Checked	Compile time (संभालना ज़रूरी)	IOException, SQLException
Unchecked	Runtime	ArithmeticException, NullPointerException

💡 क्यों संभालें?

बिना handling के एक error पूरा program crash कर देती है। handling से friendly message दिखाकर program चलता रहता है।

⚠️ आम गलती

खाली catch {} block कभी न छोड़ें — यह bugs छुपाता है। कम से कम error log करें।

सारांश

Exceptions normal flow रोकती हैं; handling crash रोकती है।
Keywords: try, catch, finally, throw, throws।
finally हमेशा चलता है; checked ज़रूरी, unchecked runtime पर।

← Back to Java Tutorial

💻 Live Code Editor

This page's programs are ready here — run them, edit them, and learn. No installation needed.

Powered by OneCompiler. The code loads into the editor automatically — press Run to see the output. If the editor does not open, open it in a new tab.