Un-checked Exceptions

Unchecked exceptions in Java, also known as runtime exceptions, do not require you to declare them using the throws clause or handle them explicitly using a try-catch block. They usually occur at runtime and are not checked by the compiler. Below are some common unchecked exceptions along with examples:

1. NullPointerException: Occurs when you try to access a method or field on a null object.

   public class NullPointerExceptionExample {
       public static void main(String[] args) {
           String str = null;
           int length = str.length(); // This will throw a NullPointerException
       }
   }

2. ArrayIndexOutOfBoundsException: Happens when you try to access an array element with an invalid index.

   public class ArrayIndexOutOfBoundsExceptionExample {
       public static void main(String[] args) {
           int[] arr = {1, 2, 3};
           int value = arr[5]; // This will throw an ArrayIndexOutOfBoundsException
       }
   }

3. ArithmeticException: Occurs when you perform an arithmetic operation that's not valid, such as dividing by zero.

   public class ArithmeticExceptionExample {
       public static void main(String[] args) {
           int result = 5 / 0; // This will throw an ArithmeticException
       }
   }

4. NumberFormatException: Raised when you try to parse a string to a number, but the string doesn't represent a valid number.

   public class NumberFormatExceptionExample {
       public static void main(String[] args) {
           int num = Integer.parseInt("abc"); // This will throw a NumberFormatException
       }
   }

5. IllegalArgumentException: Occurs when an illegal argument is passed to a method.

   public class IllegalArgumentExceptionExample {
       public static void main(String[] args) {
           int age = -5;
           if (age < 0) {
               throw new IllegalArgumentException("Age cannot be negative.");
           }
       }
   }

6. ClassCastException: Raised when you try to cast an object to an incompatible class.

   public class ClassCastExceptionExample {
       public static void main(String[] args) {
           Object obj = "Hello";
           Integer num = (Integer) obj; // This will throw a ClassCastException
       }
   }

It's important to note that while unchecked exceptions do not require explicit handling, it's still a good practice to handle them when you can anticipate them to avoid unexpected program crashes and improve the robustness of your code.