Posted in

EXCEPTION HANDLING CODING QUESTIONS IN JAVA

by admin••0•Posted inJAVA

1. Write a program to what happens if an exception is not caught in Java?

  public class ExceptionExample {
    public static void main(String[] args) {
        method1();
    }
    static void method1() {
        method2();
    }
    static void method2() {
        int result = 10 / 0; 
    }
}

Output :

Exception in thread “main” java.lang.ArithmeticException: / by zero
at ExceptionExample.method2(ExceptionExample.java:9)
 at ExceptionExample.method1(ExceptionExample.java:6)
 at ExceptionExample.main(ExceptionExample.java:3)

2. Write a program to what is the difference between throws and throw in Java?

class MyException extends Exception {
    public MyException(String message) {
        super(message);
    }
}
public class ThrowThrowsExample {
    public static void myMethod() throws MyException {
        throw new MyException(“This is a thrown exception”);
    }
    public static void main(String[] args) {
        try {
            myMethod(); 
        } catch (MyException e) {
            System.out.println(“Caught exception: ” + e.getMessage());
        }
    }
}

Output :

Caught exception: This is a thrown exception

3. How do you handle multiple exceptions in a single catch block?

     public class MultipleExceptionsExample {
    public static void main(String[] args) {
        try {
            int result = 10 / 0; 
            String str = null;
            str.length(); 
        } catch (ArithmeticException | NullPointerException e) {
            System.out.println(“Caught exception: ” + e);
        }
    }
}

Output :

Caught exception: java.lang.ArithmeticException: / by zero

4. Write a program for checked exception and unchecked exception?

public class ExceptionExample {
    public static void readFile() throws java.io.FileNotFoundException {
        throw new java.io.FileNotFoundException(“File not found!”);
    }
    public static void divideByZero() {
        int result = 10 / 0; 
    }
    public static void main(String[] args) {
        try {
            readFile(); 
        } catch (java.io.FileNotFoundException e) {
            System.out.println(“Checked Exception Caught: ” + e);
        }
        try {
            divideByZero(); 
        } catch (ArithmeticException e) {
            System.out.println(“Unchecked Exception Caught: ” + e);
        }
    }
}

Output :

Checked Exception Caught: java.io.FileNotFoundException: File not found!
Unchecked Exception Caught: java.lang.ArithmeticException: / by zero

5. Write a program to handle multiple exceptions with separate catch blocks?

       public class MultipleExceptionsExample {
      public static void main(String[] args) {
        try {
            int result = 10 / 0; 
            String str = null;
            System.out.println(str.length()); 
        } catch (ArithmeticException e) {
            System.out.println(“Caught ArithmeticException: ” + e);
        } catch (NullPointerException e) {
            System.out.println(“Caught NullPointerException: ” + e);
        } catch (Exception e) {
            System.out.println(“Caught generic Exception: ” + e);
        }
    }
}

Output :

Caught ArithmeticException: java.lang.ArithmeticException: / by zero

6. Write a Java program to show that the finally block is always executed, regardless of whether an exception occurs or not?

    public class FinallyBlockExample {
    public static void main(String[] args) {
        try {
            System.out.println(“Inside try block”);
            int result = 10 / 2; 
            System.out.println(“Result: ” + result);
        } catch (ArithmeticException e) {
            System.out.println(“Caught ArithmeticException: ” + e);
        } finally {
            System.out.println(“Finally block is always executed”);
        }
        try {
            System.out.println(“Inside another try block”);
            int result = 10 / 0; 
        } catch (ArithmeticException e) {
            System.out.println(“Caught ArithmeticException: ” + e);
        } finally {
            System.out.println(“Finally block is always executed, even after exception”);
        }
    }
}

Output :

Inside try block
Result: 5
Finally block is always executed
Inside another try block
Caught ArithmeticException: java.lang.ArithmeticException: / by zero
Finally block is always executed, even after exception

7. Write a Java program to demonstrate how an exception is propagated from one method to another using the throws keyword. Propagate an ArithmeticException from a method and handle it in the calling method?

   public class ExceptionPropagationExample {
    public static void divideNumbers() throws ArithmeticException {
        int result = 10 / 0; 
    }
    public static void main(String[] args) {
        try {
            divideNumbers(); 
        } catch (ArithmeticException e) {
            System.out.println(“Caught ArithmeticException: ” + e);
        }
    }
}

Output :

Caught ArithmeticException: java.lang.ArithmeticException: / by zero

8. Write a Java program that creates a custom exception called AgeNotValidException. Use this exception to validate a person’s age and throw the exception if the age is less than 18?

    class AgeNotValidException extends Exception {
    public AgeNotValidException(String message) {
        super(message); 
    }
}
public class AgeValidation {
    public static void validateAge(int age) throws AgeNotValidException {
        if (age < 18) {
            throw new AgeNotValidException(“Age is not valid. Must be 18 or older.”);
        } else {
            System.out.println(“Age is valid: ” + age);
        }
    }
    public static void main(String[] args) {
        try {
            validateAge(16); 
        } catch (AgeNotValidException e) {
            System.out.println(“Caught exception: ” + e.getMessage());
        }
        try {
            validateAge(20); 
        } catch (AgeNotValidException e) {
            System.out.println(“Caught exception: ” + e.getMessage());
        }
    }
}

Output :

Caught exception: Age is not valid. Must be 18 or older.
 Age is valid: 20

9. Write a Java program that uses the throw keyword to throw an IllegalArgumentException when an invalid age (less than 18) is passed to the checkAge() method?

   public class AgeValidation {
    public static void checkAge(int age) {
        if (age < 18) {
            throw new IllegalArgumentException(“Invalid age: Age must be 18 or older.”);
        } else {
            System.out.println(“Age is valid: ” + age);
        }
    }
    public static void main(String[] args) {
        try {
            checkAge(16); 
        } catch (IllegalArgumentException e) {
            System.out.println(“Caught exception: ” + e.getMessage());
        }
        try {
            checkAge(20); 
        } catch (IllegalArgumentException e) {
            System.out.println(“Caught exception: ” + e.getMessage());
        }
    }
}

Output :

   Caught exception: Invalid age: Age must be 18 or older.
    Age is valid: 20

10. Write a Java program to demonstrate how a NumberFormatException occurs when trying to convert a non-numeric string into an integer handle the exception gracefully and display an error message?

      public class NumberFormatExceptionExample {
        public static void main(String[] args) {
        String str = “abc123”; 
        try {
            int number = Integer.parseInt(str);
            System.out.println(“Converted number: ” + number);
        } catch (NumberFormatException e) {
            System.out.println(“Error: Invalid input. Cannot convert ‘” + str + “‘ to a number.”);
        }
    }
}

Output :

Error: Invalid input. Cannot convert ‘abc123’ to a number.

11. Write a Java program that causes an infinite recursion and throws a StackOverflowError catch the error and display an appropriate message?

   public class StackOverflowExample {
    public static void causeStackOverflow() {
        causeStackOverflow(); 
    }
    public static void main(String[] args) {
        try {
            causeStackOverflow(); 
        } catch (StackOverflowError e) {
            System.out.println(“Error: StackOverflowError occurred due to infinite recursion.”);
        }
    }
}

Output :

Error: StackOverflowError occurred due to infinite recursion.

12. Write a Java program that tries to allocate a large amount of memory (e.g., by creating a very large array) to intentionally trigger an OutOfMemoryError. Handle the error and display an appropriate message?

  public class OutOfMemoryErrorExample {
    public static void main(String[] args) {
        try {
            int[] largeArray = new int[Integer.MAX_VALUE]; 
        } catch (OutOfMemoryError e) {
            System.out.println(“Error: OutOfMemoryError occurred. The system ran out of memory.”);
        }
    }
}

Output :

Error: OutOfMemoryError occurred. The system ran out of memory.

13. Write a Java program to demonstrate handling exceptions with multiple nested try-catch blocks. Ensure that exceptions are caught at both the inner and outer levels of the try-catch hierarchy?

      public class NestedTryCatchExample {
      public static void main(String[] args) {
        try {
            System.out.println(“Outer try block starts.”);
            try {
                System.out.println(“Inner try block starts.”);
                int result = 10 / 0; 
                System.out.println(“Result: ” + result); 
            } catch (ArithmeticException e) {
                System.out.println(“Caught ArithmeticException in inner block: ” + e);
            }
            String str = null;
            System.out.println(str.length()); 
        } catch (NullPointerException e) {
            System.out.println(“Caught NullPointerException in outer block: ” + e);
        } catch (Exception e) {
            System.out.println(“Caught general Exception in outer block: ” + e);
        }
        System.out.println(“Program continues after exception handling.”);
    }
}

Output :

 Outer try block starts.
Inner try block starts.
Caught ArithmeticException in inner block: java.lang.ArithmeticException: / by zero
Caught NullPointerException in outer block: java.lang.NullPointerException
Program continues after exception handling.

14. Write a Java program that attempts to access an invalid index of an array, triggering an ArrayIndexOutOfBoundsException handle the exception and print a relevant message?

    public class ArrayIndexOutOfBoundsExample {
    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5}; 
        try {
            System.out.println(“Accessing element at index 10: ” + numbers[10]);
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println(“Error: ArrayIndexOutOfBoundsException occurred. Invalid index access.”);
        }
    }
}

Output :

  Error: ArrayIndexOutOfBoundsException occurred. Invalid index access.

15. Write a Java program that reads data from a file. If the file does not exist, handle the FileNotFoundException and display a message?

  import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FileNotFoundExceptionExample {
    public static void main(String[] args) {
        File file = new File(“example.txt”);
        try {
            Scanner scanner = new Scanner(file);
            System.out.println(“Reading from the file…”);
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                System.out.println(line); 
            }
            scanner.close(); 
        } catch (FileNotFoundException e) {
            System.out.println(“Error: FileNotFoundException. The file does not exist.”);
        }
    }
}

Output :

Error: FileNotFoundException. The file does not exist.

16. Write a Java program to demonstrate a ClassCastException by attempting to cast an object to an incompatible type. Handle the exception and print the error message?

       public class ClassCastExceptionExample {
       public static void main(String[] args) {
        Object obj = new Integer(100); 
        try {
            String str = (String) obj;
            System.out.println(“Cast successful: ” + str);
        } catch (ClassCastException e) {
            System.out.println(“Error: ClassCastException occurred. Incompatible type casting.”);
            System.out.println(“Details: ” + e.getMessage());
        }
    }
}

Output :

Error: ClassCastException occurred. Incompatible type casting.
 Details: java.lang.Integer cannot be cast to java.lang.String

17. Write a Java program that reads content from a file using FileReader and handles the IOException that might occur during the file reading process?

import java.io.FileReader;
import java.io.IOException;
public class FileReaderIOExceptionExample {
    public static void main(String[] args) {
        String filePath = “example.txt”;
        try (FileReader fileReader = new FileReader(filePath)) {
            int character;
            System.out.println(“Reading content from file:”);  
            while ((character = fileReader.read()) != -1) {
                System.out.print((char) character); 
            }
        } catch (IOException e) {
            System.out.println(“Error: IOException occurred while reading the file.”);
            System.out.println(“Details: ” + e.getMessage());
        }
    }
}

Output :

Error: IOException occurred while reading the file.
Details: example.txt (The system cannot find the file specified)

18. Write a Java program that demonstrates how to handle a NullPointerException. The program should attempt to call a method on a null object and handle the exception gracefully?

   public class NullPointerExceptionExample {
    public static void main(String[] args) {
        String str = null; 
        try {
            int length = str.length(); 
            System.out.println(“Length of the string: ” + length);
        } catch (NullPointerException e) {
            System.out.println(“Error: NullPointerException occurred. Cannot call method on a null object.”);
        } 
        System.out.println(“Program continues after exception handling.”);
    }
}

Output :

Error: NullPointerException occurred. Cannot call method on a null object.
Program continues after exception handling.

Leave a Reply

Your email address will not be published. Required fields are marked *