How to properly throw exceptions in Java?

Exceptions should be thrown when an abnormal situation occurs that disrupts the normal execution of the program and requires immediate handling.

Main principles:

• Use exceptions to report errors, not for flow control.
• Choose the most appropriate exception type from the standard library.
• Create custom exception classes when standard ones do not provide sufficient information.
• Include detailed information about the error cause in the exception message, including context.
• Do not catch exceptions that you cannot handle properly. It is better to propagate them up the call stack.
• Use try-with-resources blocks for automatic resource management.
• Log exceptions that you handle or propagate to higher levels.

Correct syntax: throw new MyException("Error message");

Example:

// Creating a custom exception
public class InvalidParameterException extends Exception {
    public InvalidParameterException(String message) {
        super(message);
    }
}

// Method that throws an exception
public int divide(int a, int b) throws InvalidParameterException {
    if (b == 0) {
        throw new InvalidParameterException("Division by zero is not allowed");
    }
    return a / b;
}

// Using the method and handling the exception
public void performDivision(int x, int y) {
    try {
        int result = divide(x, y);
        System.out.println("Result: " + result);
    } catch (InvalidParameterException e) {
        // Logging the error
        System.err.println("Error during division: " + e.getMessage());
        // Possibly further handling or rethrowing
    }
}

Differences between Checked and Unchecked exceptions:

Exception Type	Inherits from	Requires handling/declaration	Example
Checked	Exception (except RuntimeException)	Yes (try-catch or throws)	IOException, SQLException
Unchecked	RuntimeException	No (compiler does not require)	NullPointerException, ArrayIndexOutOfBoundsException