Java programs handling of checked exceptions.
Here are five Java programs that demonstrate the handling of checked exceptions, along with step-by-step explanations for each (Java programs handling of checked exceptions.)
Program- “1” : File Not Found ExceptionÂ
java import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; public class FileNotFoundExample { public static void main(String[] args) { File file = new File("nonexistent.txt"); try { Scanner scanner = new Scanner(file); while (scanner.hasNextLine()) { System.out.println(scanner.nextLine()); } scanner.close(); } catch (FileNotFoundException e) { System.out.println("File not found: " + e.getMessage()); } } }
Explanation:
1. Import Classes: We import File, FileNotFoundException, and Scanner from java.io and java.util.
2. Create File Object: A File object is created that points to “nonexistent.txt”, which does not exist.
3. Try Block: We attempt to open the file using Scanner. This can throw a FileNotFoundException, a checked exception.
4. Catch Block: If the exception is thrown, we catch it and print an error message.
Program- “2” : SQL Exception
java import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class SQLExceptionExample { public static void main(String[] args) { String url = "jdbc:mysql://localhost:3306/mydatabase"; String user = "username"; String password = "password"; try { Connection connection = DriverManager.getConnection(url, user, password); Statement statement = connection.createStatement(); statement.executeUpdate("INSERT INTO users_data (username) VALUES ('code pulling')"); connection.close(); } catch (SQLException e) { System.out.println("SQL Exception: " + e.getMessage()); } } }
Explanation:
1. Import Classes: We import necessary SQL classes.
2. Database Connection: We define the URL, username, and password for the database connection.
3. Try Block: Inside a try block, we attempt to establish a connection to the database and execute an SQL statement.
4. Catch Block: If any SQLException occurs (like wrong credentials), we catch it and print the message.
Program- “3” : Class Not Found Exception
java public class ClassNotFoundExample { public static void main(String[] args) { try { Class.forName("com.nonexistent.ClassName"); } catch (ClassNotFoundException e) { System.out.println("Class not found: " + e.getMessage()); } } }
Explanation:
1. Try to Load Class: We attempt to load a class that doesn’t exist using Class.forName().
2. Catch Block: If the class is not found, a ClassNotFoundException is thrown and caught, allowing us to handle the error gracefully.
java public class InterruptedExceptionExample { public static void main(String[] args) { Thread thread = new Thread(() -> { try { Thread.sleep(1000); System.out.println("Thread woke up!"); } catch (InterruptedException e) { System.out.println("Thread was interrupted: " + e.getMessage()); } }); thread.start(); thread.interrupt(); // Immediately interrupt the thread } }
Program-“4”: Interrupted Exception.
java public class InterruptedExceptionExample { public static void main(String[] args) { Thread thread = new Thread(() -> { try { Thread.sleep(1000); System.out.println("Thread woke up!"); } catch (InterruptedException e) { System.out.println("Thread was interrupted: " + e.getMessage()); } }); thread.start(); thread.interrupt(); // Immediately interrupt the thread } }
Explanation:
1. Thread Creation: We create a new thread that sleeps for 1 second.
2. Try Block: Inside the thread, we handle InterruptedException if the thread is interrupted during sleep.
3. Interrupt the Thread: The main method interrupts the thread right after it starts.
4. Catch Block: If interrupted, the exception is caught and a message is printed.
Program- “5” : Parse Exception
java public class ParseExceptionExample { public static void main(String[] args) { String number = "123a"; try { int result = Integer.parseInt(number); System.out.println("Parsed number: " + result); } catch (NumberFormatException e) { System.out.println("Number format exception: " + e.getMessage()); } } }
Explanation:
1. String to Parse: We define a string that cannot be converted to an integer.
2. Try Block: We try to parse the string using Integer.parseInt().
3. Catch Block: If it throws a NumberFormatException, we catch it and print an appropriate message.
These programs illustrate how to handle various checked exceptions in Java, showing the importance of managing errors effectively to create robust applications.