Java | Throwing and propagating exceptions

Java provides a mechanism for handling errors and exceptional situations called exceptions. An exception is an object that describes an error or an abnormal condition that has occurred during program execution. Exceptions can occur for various reasons, such as incorrect input, network problems, or system errors. Java also provides a way to handle these exceptions using the try-catch-finally block.

The try-catch-finally block

The try-catch-finally block is a mechanism for handling exceptions in Java. It consists of three parts:

• The try block contains the code that may throw an exception.
• The catch block catches the exception and handles it.
• The finally block is executed regardless of whether an exception is thrown or caught.

Here’s an example of how to use the try-catch-finally block in Java:

try {
    // code that may throw an exception
} catch (Exception e) {
    // code to handle the exception
} finally {
    // code that is executed regardless of whether an exception is thrown or caught
}

Throwing an exception

You can also create and throw your own exceptions in Java using the throw statement. To do this, you must create a new instance of the exception class and then use the throw statement to throw it. Here’s an example of how to throw an exception:

public class MyException extends Exception {
    public MyException(String message) {
        super(message);
    }
}

public class MyProgram {
    public void myMethod() throws MyException {
        throw new MyException("An error occurred!");
    }
}

In this example, we define a custom exception class called MyException that extends the Exception class. We also define a method called myMethod that throws the MyException exception.

Propagating an exception

When an exception is thrown in a method, it can be propagated to the calling method using the throws keyword. If a method throws an exception, it must declare it in its signature using the throws keyword. Here’s an example of how to propagate an exception:

public class MyProgram {
    public void myMethod() throws MyException {
        // code that may throw an exception
    }

    public void myOtherMethod() throws MyException {
        myMethod();
    }
}

In this example, we define two methods, myMethod and myOtherMethod. myMethod may throw an exception, so it is declared with the throws keyword in its signature. myOtherMethod calls myMethod, so it must also declare the MyException exception in its signature.

In summary, Java provides a mechanism for handling exceptions using the try-catch-finally block. You can also create and throw your own exceptions using the throw statement, and propagate exceptions to calling methods using the throws keyword.