Exception handling in Java

What Is an Exception?

An exception is an unwanted event that interrupts the normal flow of the program.

Examples:

• Division by zero
• Accessing an invalid array index
• File not found
• Null pointer access Java uses objects to represent exceptions.

**⭐ Types of Exceptions

1. Checked Exceptions**

• Known at compile time
• Must be handled using try-catch or declared with throws

*Examples:
*

• IOException
• SQLException
• FileNotFoundException

1. Unchecked Exceptions

Known at runtime
Occur due to logical errors in the code

Examples:

• ArithmeticException
• NullPointerException
• ArrayIndexOutOfBoundsException

1. Errors

Serious issues beyond the control of the program

Example:

• OutOfMemoryError
• StackOverflowError

⭐ Exception Handling Keywords
Keyword Meaning

• try -Wraps code that may throw an exception
• catch -Handles the exception
• finally -Always runs (even if exception occurs)
• throw -Throw an exception manually
• throws- Declare an exception in method signature

⭐ Basic Example
public class Example {
public static void main(String[] args) {
try {
int a = 10 / 0; // risky code
} catch (ArithmeticException e) {
System.out.println("Cannot divide by zero!");
} finally {
System.out.println("This always executes.");
}
}
}

Output:
Cannot divide by zero!
This always executes.

⭐ Multiple Catch Blocks
try {
int arr[] = new int[5];
arr[10] = 50;
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Invalid array index!");
} catch (Exception e) {
System.out.println("Other exception occurred.");
}

⭐ throws Keyword Example
void readFile() throws IOException {
FileReader fr = new FileReader("data.txt");
}

⭐ throw Keyword Example
if(age < 18){
throw new ArithmeticException("Not eligible to vote");
}

⭐ Why Use Exception Handling?

• Prevents program crashes
• Improves reliability
• Separates error-handling code from normal code
• Helps recover from unexpected situations