Try-catch structure

How to Handle Exceptions

From the previous chapter, you may have understood that exceptions completely halt the program's execution. Such an outcome is not desirable for us because we need the program to continue running without crashing.

Simply removing exceptions is not an option, as in that case, the program would work incorrectly. Therefore, we need to learn how to handle errors using the try-catch structure.

Let's take a look at the syntax of such a structure and understand how it captures errors:

try Block: This block contains the code that might generate an exception. During execution, if any statement within the try block throws an exception, the rest of the block's code is skipped, and the control moves to the corresponding catch block(s) to handle that exception;
catch Block: This block is used to handle the exception. It must follow the try block. If the type of exception thrown matches the type declared in the catch block, the code inside this block is executed. There can be multiple catch blocks associated with a single try block, each catching and handling different types of exceptions.

In simpler terms, we attempt to execute the code, preparing to catch an exception. If we catch an exception, the code execution doesn't stop but continues with the operation specified in the catch block. If there's no exception, the operation is executed successfully without entering the catch block.

Handling ArithmeticException

In the previous chapter, we implemented a division method that throws an arithmetic exception in case of division by zero. Here's what this method looks like:

Now, let's handle this exception when calling the method using a try-catch structure:

main


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package com.example;

public class Main  {
    public static double divide(int numerator, int denominator) throws ArithmeticException {
        if (denominator == 0) {
            throw new ArithmeticException("Division by zero is not allowed.");
        }
        return (double) numerator / denominator;
    }

    public static void main(String[] args) {
        try {
            double result = divide(10, 0);
            System.out.println(result);
        } catch (ArithmeticException e) {
            System.out.println("You can't divide by zero!");
        }
        System.out.println("The program is continues its execution");
    }
}

As you can see, we attempt to perform division by zero, but we do it within the try block. In the catch block, we catch the ArithmeticException and give it an alias "e" so that we can use this object in the future (remember, exceptions are objects, right?).

This way, the exception doesn't halt the program's execution since we've handled it. Now, in the event of an exception being thrown, the program notifies the user with console output and continues its execution.

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Seção 3. Capítulo 2