You are using the pattern AutoClosable to create your PreparedStatement, in this pattern you create an instance of an obejto that implements the interface Closable in the try, whenever the try ends it gives a close automatically on the created objects.The code below will work:public ContaCorrente getConta(int agencia, int numConta) { String query = "SELECT * FROM CONTACORRENTE" + " WHERE AGENCIA = ? AND NUMERO = ?"; ResultSet rs = null; try (PreparedStatement st = ConexaoComBd.getConectora().getConexao().prepareStatement(query);) { st.setInt(COLUNA_AGENCIA, agencia); st.setInt(COLUNA_NUMCONTA, numConta); rs = st.executeQuery(); System.out.println("Result set dentro do try catch: "+rs);//AQUI TUDO CERTO ContaCorrente c = montarConta(rs); return c; } catch (SQLException e) { System.err.println("Erro no banco de dados ao consultar conta corrente. Tente novamente" + "ContaCorrenteDAO Linha67"); System.err.println(e); } catch (Exception e2) { System.err.println("Erro geral ao consultar conta corrente. Tente novamente "); } System.out.println("ResultSet após o try catch:" +rs); //AQUI ELE ESTÁ null return null; }

I found that it is not possible to catch Fatal Errors with catch because this kind of error makes the program stop.Then I redesigned the function that connects to MySQL starting by disabling this type of error with ini_set('display_errors', 0); and using the PDO PDOException error treatment:function connect() { try { ini_set('display_errors', 0); $pdo = new \PDO("mysql:host=localhost;dbname=BassamBrasil;charset=utf8", 'root', 'root'); $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ); return $pdo; } catch(PDOException $e) { //cho 'ERROR: ' . $e->getMessage(); echo 'ERROR: Error connecting to database'; } } Well, I believe this is the best way to show only the personalized message.

Throwable is the base interface for any launchable object.Source: http://php.net/manual/pt_BR/class.throwable.php Exception is the base class for all Exceptions No PHP 5, and the base class of all user exceptions in PHP 7.Source: https://secure.php.net/manual/pt_BR/class.exception.php In short, capturing the interface is equivalent to capturing all classes that implement it...- I don't know how I can call them.Imagine the following scenario: you http://php.net/manual/pt_BR/language.exceptions.extending.php \Exception in your project and, when you want to stop running something and simply display the message, launch that class. But if any fatal error occurs, literal exception, and etc, you display the error message and terminate the full script execution. Example:<?php try { bar(); if (!baz()) throw new MinhaExcecao('A função baz() retornou falso.'); } catch (MinhaExcecao $e) { echo $e -> getMessage(); // O script vai continuar a ser executado... } catch (PDOException $e) { die('PDO lançou uma exceção. Há algo errado na conexão/consulta do banco de dados.'); // O script não vai continuar a ser executado... } catch (Throwable $e) { die('Capturado alguma classe que implementa a interface Throwable'); // O script não vai continuar a ser executado... } echo 'foo'; If the function baz() return false, will fall into the block catch (MinhaExcecao $e) with echo and then the script will continue on echo 'foo';... In other cases, the execution will be fully interrupted by the function call die().It is worth remembering that the catch work like a waterfall. When launching some object, it will be captured in the first block catch compatible with the class/interface launched. In this way, your custom class must be captured first or before your parent class/interface, or else will not arrive in catch intended.There's still the block. I used it PHP as a reference, but the theory is equivalent in the main programming languages. Maybe there are some small differences. .

The best way to validate in XML files is by using a validation scheme.DTDs are usually used. A basic tutorial in using DTDs for XML file validation can be found https://lxml.de/validation.html . More information about DTDs can be found https://en.wikipedia.org/wiki/Document_type_definition . More information about other XML validation methods can be found https://en.wikipedia.org/wiki/XML_validation .In the above case, you try to access the fields of your XML. There are more general ways to perform XML parsing as implemented https://github.com/martinblech/xmltodict . Perhaps this link is enough to solve your problem more elegantly.

Do not use while for this, use a function. The while is asynchronous with setTimeout and will generate a process bottleneck, causing the crash. Using a function you can do synchronized, just calling the setTimeout again after the set time:(function checa(){ setTimeout(function() { try{ document.querySelector('.department-info').click() } catch(e) { console.log('Retrying in 60 seconds...') //error handling checa(); // chama novamente a função após o tempo } }, 60000) })(); // função auto-executada 2-second test:By clicking on body, will insert the button with the class .department-info and shoot the click :$("body").click(function(){ $(this).html('<button class="department-info" onclick="alert(\'Clicado\')">OK</button>') }); (function checa(){ setTimeout(function() { try{ document.querySelector('.department-info').click() } catch(e) { console.log('Retrying in 2 seconds...') //error handling checa(); } }, 2000) })();<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> Clique aqui para adicionar o botão

First, it depends on what is calling a layer. If they are code layers within the same application, yes, the exception will bubbling until someone captures it, ultimately the .NET captures it for you and does something (shows the error default).Exception is a complicated mechanism, it is a goto that you do not know or where it will stop. You are not required to deal with failure (unlike what many say about this mechanism) and do not know who will deal with it.If you're right, you won't lose stack, but for this it is important not to get caught to throw the exception again. The problem is that in codes that abuse exception and use as validation mechanism it is common to do this, especially in layers, your tendency will be to capture in one layer to throw something else into another layer.Often launch exceptions can be https://pt.stackoverflow.com/q/354926/101 . It is very complicated to make the exception to be something natural, one of the reasons for not using it for flow control, as it seems to be the case you are wanting to do, because if they were used for exceptional situations probably would not be living this dilemma.Without a deep analysis it is complicated to give a definitive answer to the problem, and even more generic solutions cause controversy, I have seen people defending one thing or another.If you use right the exception should not go beyond the layer where it originates, another reason not to worry about stack. In the repository it seems a suitable place to capture some types of well-specific exceptions.In the business layer should rarely have exceptions because there you will only have validations, you will only have things that you have control, which failing is likely expected, is not exceptional.But it is always possible to do something different. If it is controller that mounts what will be shown to the user, there can be the suitable location to capture a true exception. There are controversies as to this, but one of the advantages of the exception is not having to go through, you let it burst until you arrive at the place where you can do something useful, and most of the time it is when you will interact with the user (although the controller do not be the place of interaction, it is the last code that will run in this layer of the solution, the side backend).

It turns out that there is an exception to the type https://docs.oracle.com/javase/7/docs/api/java/util/InputMismatchException.html makes content not consumed. Soon if you are trying to read an integer and the user puts a text as "teste" an exception and the text "teste" Keep going. This means that when come back again nextInt to read again, get the same exception again. The solution is to clear what was forcing a reading in String for example, using nextLine:try { opcao = in.nextInt(); System.out.print("\n"); checar =1; } catch(Exception e) { in.nextLine(); //"limpa" o que ficou por ler que não era inteiro System.err.println("Você digitou um caractere inválido! Tente novamente "); } It is however important to mention that you must always capture only the exception you are interested in and not all how you are doing using Exception, because in some cases you can get other exceptions that you would not be waiting and give the same treatment without realizing. Then could rewrite capturing only InputMismatchException:try { opcao = in.nextInt(); System.out.print("\n"); checar =1; } catch(InputMismatchException« e) { // ^--- captura apenas o tipo que interessa in.nextLine(); System.err.println("Você digitou um caractere inválido! Tente novamente "); }

Each case is a case, but in general nesting try is not the most suitable. This probably indicates that you are capturing more exceptions than you should.Anyway, normally you just want to give an exception treatment. try catch is not a normal flow control, so it rarely makes sense to have them nested. The release of an exception is a long jump, that is, he goes to a distant place, possibly unknown. So it doesn't matter so much where the catch, it can, and it is very common, that it is not in the current function. This is normal.The important thing when an exception is released is that it is captured by some catch somewhere in your application code, anywhere that is suitable to capture and do something useful to try to recover from the error. Don't worry about the flow, it will already be "disvirtuated" of your normal after the throw.This capture can be unique throughout the system, only for log the error and present in a "good" way to the user. Do not abuse the capture of errors. See more about this in https://pt.stackoverflow.com/a/30168/101 . It is important to note that using a catch doesn't do miracles, he doesn't solve problems by himself. On the contrary, your exaggeration makes you hide mistakes.Then in his example the "most correct" would be:try { $bancoDeDados = new Bd(); $bancoDeDados->createCreateEntidade($valor1,$valor2); $this->geraPdf($valor1,$valor2); } catch (PDOException $e) { //faz alguma coisa } catch(ExceptionSeiLa $e) { //faz alguma coisa } https://github.com/bigown/SOpt/blob/master/PHP/Syntax/NestedTryCatch.php If you give a problem PDOExcption when to call Bd() or createCreateEntidade he will divert to the first catch. If it occurs ExceptionSeiLa, probably generated by the method geraPdf, the deviation will be for the second catch.One catch does not need and in general should not be associated with a try exclusive. You should treat all the exceptions you need to treat at this time in a dull way, and not once in a nested way.Of course. can there is some situation that nesting is useful. But it's unusual.If an exception is generated before performing geraPdf(), probably by Bd() or createCreateEntidade, certainly it will not be executed, the exception generates a deviation before reaching it and does what you want. Depending on what you want, maybe even the second catch be unnecessary.But avoid abusing the capture of exceptions that you can't do anything useful. I understand that you have just made a simple example, but if you capture an exception and don't do anything with it, something is wrong.Personally if I can avoid the use of exception, I do. If I can check with if If there's something wrong, I'll do it. I only use exception if:the algorithm with if get more confused than with try catchcan generate a https://pt.stackoverflow.com/q/159342/101 or considerable loss of performancethe API obliges to do this (there is no other way available to "touch" the error).This last case is very common in Java. Language culture and environment encourage the use of exceptions.I don't have much experience with the new PHP APIs, but what I've always used from PHP, exceptions are rarely needed. It always has a way to resolve the issue without its use. But PHP started without exceptions if it worked well without them. Of course its addition brought new perspectives but also brought much abuse.You can still fall in the first two cases. In the first can be more advantageous to prefer the exception and in the second can be required to have the correct solution and with proper performance.

O len returns a value that starts from 1, and not from 0. However, the position count starts from 0.while i<=len(bolas): Let's assume that len(bolas) is equal to 10: The positions of the balls are from 0 to 9, which closes 10 numbers ( len value), the i starts in 0 and goes up to 10 (pois while i<=len(bolas)), however, the array does not go to position 10, but until 9.I think to change while i<=len(bolas): by while i<len(bolas): will solve your problem, not needing so try/except.

probably forgot a point and virgula:Here’s an example http://php.net/manual/pt_BR/language.exceptions.php <?php function inverse($x) { if (!$x) { throw new Exception('Divisão por zero.'); } return 1/$x; } try { echo inverse(5) . "\n"; echo inverse(0) . "\n"; } catch (Exception $e) { echo 'Exceção capturada: ', $e->getMessage(), "\n"; } // Execução continua echo "Olá mundo\n"; ?>

In this case there is no reason to do that. It is. https://pt.stackoverflow.com/a/56299/101 , and in the worst possible way. If an exception will be captured in the function that is released is wrong in 100% of cases. The exception is a way to divert the execution of the code far from where it is.If the exception is captured outside is usually wrong in most cases people do. If used right has very little try-catch in the code. And https://pt.stackoverflow.com/q/30124/101 .This case would be simpler so:public function cadastrarUsuarios(parametros) { mysqli_query($this->conexao,"INSERT...."); if (mysqli_affected_rows($this->conexao) > 0) { $_SESSION["Sucesso"] = time() + 3; return "<script>window.location.href='pagina.php';</script>"; } else { $_SESSION["Erro"] = time() + 3; return NULL; } } $resultado = $metodos->cadastrarUsuarios(parametros); if (is_null($resultado)) echo "deu erro"; else echo $resultado; https://github.com/maniero/SOpt/blob/master/PHP/Exception/FlowControl.php In case PHP might not use NULL, could be a boolean. In fact anything that is not expected, could even use the string empty if it is guaranteed that in normal condition would never have a result like this, but I have doubts if this can be guaranteed in this case.See https://pt.stackoverflow.com/q/21767/101 .Also: https://pt.stackoverflow.com/q/21933/101 https://pt.stackoverflow.com/q/141899/101 https://pt.stackoverflow.com/q/15261/101

After some research and help from some friends I got what I needed and I have come to share with you the final result, I hope you can help someone.Code commented, follows:// ATRIBUI A PDO CONEXION $connection = Connection::getInstance(); $crud = Crud::getInstance($connection); // DATA OF THE FORM $IdInterface = (isset($_POST['IdInterface']) ? $_POST['IdInterface'] : ''; $IdUsuario = (isset($_POST['IdUsuario']) ? $_POST['IdUsuario'] : ''; $Servicos = (isset($_POST['Servicos']) ? $_POST['Servicos'] : ''; try { // INICIALIZA TRANSACTION $connection->beginTransaction(); // BUSCAND USER REGISTERS X SERVICE $sql = "SELECT" _ IdServico, _ IdUsuaria FROM _ _ Servico ON (gasServico). IdServico = gasUsuarioServico. IdServico) WHERE (gasUsuarioServico). IdServico = gasServico. IdServico) _ (gasUsuarioServico). IdUsuario = ? (gasServico.) IdInterface = ?)"; $stm = $conexao->prepare($sql); // _ $stm->bindValue(1, $IdUsuario, PDO::PARAM_INT); $stm->bindValue(2, $IdInterface, PDO::PARAM_INT); $stm->execute(); $Resdated = $stm->fetchAll(PDO::FETCH_OBJ); // CONTACT RETORED REGISTERS $conProd = count($Resdated); _ $stm->closeCursor(); // DELETING USER REGISTERS X SERVICE foreach ($Added to $DadosUsuarioServico) { try{ $IdUsuario = $DadosUsuarioServico->IdUsuario; $IdServico = $DadosUsuarioServico->IdServico; ♪ WHERE 'IdUsuario' = ? _ $stm = $conexao->prepare($sql); $stm->bindValue(1, $IdUsuario, PDO::PARAM_INT); $stm->bindValue(2, $IdServico, PDO::PARAM_INT); $stm->execute(); } catch(PDOException $erro) { // DESFAZATION ATUAL TRANSPORT $connexion->rollBack(); $erro = $erro->getMessage(); $return = array('code' => '0', 'mesage' => ' Error when deleting services. Try again [1]. $connection = null; // MESSAGE RETOR echo json_encode($return); exit(); ) ) // GRAVING THE CHECKS MARCADOS if ($Servicos != ") { try { $$ Servicos as $IdServico) { // INSERT $crud = $conexao->prepare("INSERT INTO gasUsuarioServico (IdUsuario, IdServico) VALUES (?, ?)'); $crud->bindParam(1, $IdUsuario, PDO::PARAM_INT); $crud->bindParam(2, $IdServico, PDO::PARAM_INT); $crud->execute(); ) } catch(PDOException $erro) { // DESFAZATION ATUAL TRANSPORT $connexion->rollBack(); $erro = $erro->getMessage(); $return = array('code' => '0', 'mesage' => ' Error when entering the services. Try again [2]. $connection = null; // MESSAGE RETOR echo json_encode($return); exit(); ) ) // BUSCAND USER REGISTERS X SERVICE $sqlInterface = "SELECT" gasUser Servico. IdUsuario, gasUsuarioServico. IdServico, gasServico. IdInterface FROM gasUser Service INNER JOIN gasServico ON (gasUsuarioServico. IdServico = gasServico. IdServico) WHERE (gasUsuarioServico. IdUsuario = ? (gasServico. IdInterface = ?)"; $stm = $connection->prepare($sqlInterface); // _ $stm->bindValue(1, $IdUsuario, PDO::PARAM_INT); $stm->bindValue(2, $IdInterface, PDO::PARAM_INT); $stm->execute(); $ResdatedInterface = $stm->fetchAll(PDO::FETCH_OBJ); // CONTACT RETORED REGISTERS $conSqlDel = count($ResDadosInterface); _ $stm->closeCursor(); // DELETING USER REGISTERS X INTERFACE SE EXISTI SOBRAS if ($conSqlDel == 0) { try { $sql = "DELETE FROM gasUsuarioInterface WHERE gasUsuarioInterface. IdUsuario = ? _ Interface. IdInterface = ?"; $stm = $conexao->prepare($sql); $stm->bindValue(1, $IdUsuario, PDO::PARAM_INT); $stm->bindValue(2, $IdInterface, PDO::PARAM_INT); $stm->execute(); } catch(PDOException $erro) { // DESFAZATION ATUAL TRANSPORT $connexion->rollBack(); $erro = $erro->getMessage(); $return = array('code' => '0', 'mesage' => ' Error when deleting user interfaces. Try again [3]. $connection = null; // MESSAGE RETOR echo json_encode($return); exit(); ) // BUSCAND INTERFACES REGISTERS $sqlInterfaceReg = " _ gasUser Interface WHERE (gasUsuarioInterface. IdUsuario = ? (gasUsuarioInterface. IdInterface = ?)"; $stm = $connection->prepare($sqlInterfaceReg); // _ $stm->bindValue(1, $IdUsuario, PDO::PARAM_INT); $stm->bindValue(2, $IdInterface, PDO::PARAM_INT); $stm->execute(); $ResueInterface = $stm->fetchAll(PDO::FETCH_OBJ); $countInsert = count($ResUsuarioInterface); _ $stm->closeCursor(); if ($countInsert == 0) { try { // INSERT USER X INTERFACE $crud = $conexao->prepare("INSERT INTO gasUsuarioInterface (IdUsuario, IdInterface) VALUES (?, ?)"); $crud->bindParam(1, $IdUsuario, PDO::PARAM_INT); $crud->bindParam(2, $IdInterface, PDO::PARAM_INT); $crud->execute(); } catch(PDOException $erro) { // DESFAZATION ATUAL TRANSPORT $connexion->rollBack(); $erro = $erro->getMessage(); $return = array('code' => '0', 'mesage' => ' Error when deleting user interfaces. Try again [4]. $connection = null; // MESSAGE RETOR echo json_encode($return); exit(); ) ) ) $connection->commit(); } catch (Exception $e) { // DESFAZATION ATUAL TRANSPORT $connexion->rollBack(); $return = array('code' => '0', 'mesage' => ' An error occurred in the recording, try again [5]. ::$erro'); $connection = null; // MESSAGE RETOR echo json_encode($return); exit(); ) $return = array('code' => '1', 'message' => ' Access law successfully inserted'); // FECHA CONEXION $connection = null; // MESSAGE RETOR echo json_encode($return); exit();

To solve this problem, and similar ones, you need to do script error treatment. There are basically two ways to do this:1. tryCatch2. package purrrUtilizing the tryCatchThis is an example of my own practice:for (i in 1:nrow(pg_amostra)) { pagina <- tryCatch({ pagina = html_session(pg_amostra$http[i]) }, warning = function(w) { print('Aviso!') Sys.sleep(0.3) pagina = html_session(pg_amostra$http[i]) }, error = function(e) { print('Erro') texto <- '' }, finally = { Sys.sleep(0.3) texto <- html_nodes(pagina, css = '.corpoTextoLongo') %>% html_text() }) print(i) assign(paste("texto", i, sep = ""), texto) } Here in the table pg_amostra there is information about several pages and the url of these pages is in the column http.SOLUTION WITH purrFor the treatment of errors I having to always use the purr because it is simply much easier. In this example, also from my own practice, I create a function that extracts a piece of text from a page.pega_texto <- function(url) { texto <- read_html(url, encoding = 'iso-8859-1') %>% html_nodes(css = '.corpoTextoLongo') %>% html_text() pb$tick() return(texto) } NO, if the read_html() fail the entire script can stop. So I'll "envolve" the function with the possibly() of the purr in order to treat possible errors by simply generating a NA.pega_texto <- possibly(.f = pega_texto, otherwise = NA_real_, quiet = T) From now on, if I use this function and some mistake happen it will always return one NA. Then by storing the results in a table, or I will have a text or a NA. Just redo the search ONLY urls that returned NA.

How does the run stream work in a try/catch/finally block in the example below?You will enter the try and play an exception. As expected, println after makeException() will not be executed. After that, program will run the block catch(ExceptionBeta and after that the block inside finally.The block finally always performs at the end, regardless of an exception being thrown or not (it is particularly useful to make "cleaning" at the end of the method)I would also like to know, in this same code, how to make more than one exception, in addition to ExceptionBeta In Java, and in all the programming languages I know with exceptions, only gives an exception at a time.One possibility is to create a single class for the exception and pass the list of errors as one of the fields of that class.Is there a possibility of using logical operators in catch? for example: catch(ExceptionAl alphaphaEx && ExceptionBeta betaEx) {...}I don't know what you expect to do in this case. Anyway, I don't think Java supports something like that.As for "or", to treat more than one type of exception in a single catch, in Java 7+ there is the syntax | for this:catch (IOException|SQLException ex) { logger.log(ex); throw ex; } http://docs.oracle.com/javase/tutorial/essential/exceptions/catch.html If you are with an older version of Java, the best you can do is capture a superclass of your classes or make multiple catches even. In the latter case you can try to create an internal little scare to avoid duplicating code.} catch(ExceptionAlpha alphaEx) { tratarExcecao(); } catch(ExceptionBeta betaEx) { tratarExcecao(); }

Exceptions are a form of deviation, as well as ifs, breaks, returns, etc. Its usefulness is to allow a code to be stopped if it has no conditions to continue, conveniently and organizedly.Suppose Java has no exceptions. If the method a calls the method b, who calls c that calls FileReader.read, what happens if there is an error in reading?The method c You have to stop because you can't keep going without the data read. He returns;The method b must know that the method c failed; for that, c has to return a special error code - interfering in your normal return value - and b have to test for this code using one if (e.g.);The method a must know that the method b failed; etc.Somewhere, this error will have to be dealt with - even if it is in main (or Thread.run), to abort the program with error code. What exceptions do is allow the execution flow to deviate [almost] directly from the exact point where the error treatment is possible, without the programmer having to do anything else. More: they collect and store various information about the error, as which methods were running and in which line they were, allowing to generate a report that allows the programmer to more easily discover its cause.When declaring an object, if the programmer predicts that a failure in the execution of the method may occur, it will launch a type object Exception. (right?)Not necessarily. It can do this if the error is detected by its own logic, and this deviation is convenient for the caller. It may also not release exceptions directly, but allow your code (i.e. the other functions that this method calls) to launch them - declaring this in your subscription if necessary (throws ExceçãoX, ExceçãoY). Or he can do something else, like returning an error code, try to treat the exception alone, log somewhere... Depends on the case.In general, the "right thing" to do is to throw/allow an exception even - perhaps unchecked (more on this ahead). Returning an error code complicates the call form, and logging the error makes system customization harder (i.e. if you do not want that this error is logged in, and the method does alone, by its default, this can hinder its use or require some "gambiarra" to circumvent/undo it. If you have no good reason to divert it, do not deviate: use exceptions even.I wanted to understand how the capture and release of the exception works.Returning to the Methods Example a, b and c, say a is prepared to treat the exception E, while b It's not. As the methods are being called, the execution contexts (i.e. local variables, current instruction, etc.) of them are being placed in the pile. Usually, b would have to run until the end before the control returns to a, the same for c in relation to b. But if c finds this exceptional condition - and decides to launch E - The following happens:c creates an instance of the object E, passing the parameters you need;The flow of execution c is interrupted where it is, i.e. your code does not finish running;If c has a block try/finally or try/catch/finally, and the exception was released within try, he performs the finally;c It's a mess. Usually, b I would continue to run where it stopped, but that's not what happens. The exception release process has not yet ended.If b has a block try/finally or try/catch/finally, and c was called inside try, he performs the finally;b It's a mess. Usually, a would continue running from where it stopped, but the process of release of the exception has not yet finished.How b was called inside a block try/catch or try/catch/finally, and E is present in one of the clauses catch, this block is executed.The exception release process is over. The code continues from the block catch forward.Why the RuntimeException and their subclasses are not verified by the compiler.There are two types of exception: checks (Check) and not checked (unchecked). Ideally - from the point of view of Java designers - no method should behave unexpectedly; or it should succeed, or fail in an orderly and consistent manner. As methods usually call other methods, each should be responsible for behave well even in the presence of errors in the methods called. Thus, each method would need to be aware of the exceptions that its components may release, and or treat them or propose them to the caller method. For this to be possible, the caller method has to be aware that this method can release exceptions X, Y and Z, and prepare accordingly.In theory it is a beauty, but in practice this is inviable. There are errors that can occur in any method, and it would be a waste to be declaring them all the time. JVM's memory may end, for example. Or in a division, the divider can be zero. If we were to take into account all these possibilities, the signature of our methods would become gigantic! And to make things worse, it is very unlikely that the caller method will be able to recover from, say, a OutOfMemoryError - anything he tried to do would spend more memory and generate others OutOfMemoryErrorTurning a snowball...That is why there are exceptions unchecked: for disobey the methods of declaring that this exception is possible, but still allow any of them to try to treat it if they think it gives account. A RuntimeException is the base class for all of them except for Error - which generally denotes a more serious condition that can hardly be treated by any method.Note: it is better to use exceptions Check (that inherited from Exception) or unchecked (that inherited from RuntimeException)? I can't tell you. It is a balance between the security of the code and its concision/expressivity. try/catchis too much and your code becomes unreadable, try/catches of less and no one knows more than errors can occur in a method. It is a situation similar to static typing (with or without generic types) vs. duck typing vs. Dynamic typing: gains on one side and gets lost on the other. .If the try/catch block is used only to treat exceptions or if there is other purpose of use.Theoretically you could [ab]use it to simulate a goto, but in general not, it's just to treat exceptions even. It should be noted that in Java the treatment of exceptions is relatively expensive, so that it is often preferable to use "normal" control streams even [for non-exceptional codes], even if this complifies a little your code. Other languages (e.g. Python) already use them for more common situations - for example the idiom (idiom) "do not check the parameters before calling the function, simply call it and if you are not successful capture the exception". It should be avoided in Java (even why try/catches are not exactly concise in my opinion...).Already try/finally and try/catch/finally, is also used to deal with exceptions, even if not exactly to "treatment them". Consider this code:try { String linha = leitor.readLine(); int x = Integer.parseInt(linha); } catch(IOException ioe) { ... } finally { leitor.close(); } In this case, we want the reader to be closed no matter what happens: if the code succeeds, if it launches a IOException, or if he throws any other exception. The important thing is not to forget it open. For even if one NumberFormatException for released on try, and he doesn't even get into catch, finally will still perform (before the exception propagates to the caller method)....and in the case of a multi-exceptional method?As already said, the code of try (or all method code if the exception occurs outside of one try) is interrupted when an exception occurs, jumping to a catch or one finally. If he falls in one catch, then it is considered that the treatment of the exception was done successfully, and the block code catch is treated as a normal code - and can even throw another exception, without any relation with the original exception.If he falls in one finally, on the other hand, we have a problem: finally is not the "destination" of the exception, only a "stop point". If he also produce an error, what should go pro method caller - the original or the new? The solution Java gives to this impasse is the following: the new method is released, but the exception holds a reference to the original exception. It is said in this case that the exception B was "caused by" the exception A. You can access A through B.getCause(). In this case, it is important to emphasize that the caller method needs to treat B - if he just takes care of A, the execution will not enter the block catch.And lastly what is the class Throwable?As already said, there are two types of "errors" in Java: Errors Exceptions. The class Throwable is the superclass of both, created to allow code to treat both simultaneously. "normal" programmers in general should not try to treat Error - since it is a serious failure that will only be circumvented if you know what you are doing well. So there is no sense in using catch Throwable - it is better to take only Exception even (if it is a generic error treatment code) or, better yet, take only the exceptions you can even treat (and propagate all the rest).Some references: http://docs.oracle.com/javase/tutorial/essential/exceptions/chained.html (on exceptions caused by other exceptions) http://docs.oracle.com/javase/tutorial/essential/exceptions/runtime.html (on use or not exceptions unchecked in its code - obviously, Java authors hang on the security side to the detriment of the concision; others disagree)

Exception has nothing to do with object-oriented language, these concepts are completely orthogonal. There is spoken language What has no exception and non-OO language that has the exception.There are schools, that is, a lot of people who have an opinion, about how to use it. Each language tends to recommend one more thing or another.More modern languages tend to avoid the use of exceptions. It is true that they have not become mainstreamHowever, it is more for market issues. From the engineering point of view it is already considered an error to have exception in language, especially in the way they are implemented.C# began adopting Java's posture and abusing exceptions, soon understood that there were several cases where it made no sense to have exceptions and started creating https://pt.stackoverflow.com/q/21767/101 . I have one https://pt.stackoverflow.com/a/13611/101 in most cases.Note that the origin of C# exceptions has even to do with C++ and in this language it is common that teams prohibit the use of exceptions.One reason not to abuse exceptions is https://pt.stackoverflow.com/q/5888/101 , especially in C#.If the situation is exceptional, that is, it almost never happens, or if it happens is programming error and will only occur in tests or in production by a lapse of the programmer, all right. If you are accessing an external feature or that the programmer has little control and that it may fail, it makes sense to have an exception. If what you expect is the error is not an exceptional situation. Data inputs are expected to come wrong, it is not an exception to come wrong. https://pt.stackoverflow.com/a/56299/101 .In this example all this can be replaced by:if (Autenticacao.Validador(senhaNumerica)) { return (Autenticador.Senha = true); } else { WriteLine("Senha não segue regras."); return false; //indica que não autenticou } It has other ways to do this without exception, better mechanisms do not lack.Obviously if an exception is released all validations were made within the class. Then make them and return a mistake, just don't throw the exception. The mistake in the top code is trying to do what the class already does for you.An example using the exception of a way that no one uses and is valid, although I do not think it appropriate to do it (people do not use because it is inadequate, it is because they do not know how to do it), more like curiosity:if (Autenticacao.Validador(senhaNumerica) is SenhaException excessao) { Autenticador.Senha = true; return true; } else { WriteLine($"Senha não segue regras. Motivo: {excessao.Message}. Veja o erro\n{excecao.StackTrace()}"); return false; } public SenhaException Validador(string senha) { if (!int.TryParse(SenhaNumerica, out var senhaConvertida)) return new SenhaException("A senha não é numérica"); if (senha.Length <= 5) return new SenhaException("Senha não numérica."); if (senhaConvertida[0]) < 4) return new SenhaException("Não pode começar com número abaixo de 4."); if (!senha.Any(ch => !Char.IsLetterOrDigit(ch)) return new SenhaException("Não foi encontrado nenhum caractere especial"); } Obviously, I would need to create the SenhaException probably inherited from https://docs.microsoft.com/en-us/dotnet/api/system.systemexception?WT.mc_id=DOP-MVP-5002397&view=net-5.0 .Of course you may not have control over the class, you cannot fix your architectural error. Then take the exception. This kind of exception is what https://docs.microsoft.com/en-us/dotnet/api/system.applicationexception?WT.mc_id=DOP-MVP-5002397&view=net-5.0 , so by wrong decision of someone you are required to do this.Just don't go https://pt.stackoverflow.com/q/30124/101 . In general the programmer does this by ignorance and laziness, especially the last, because several programmers here even read that they should not do this and continue to do it. Exception may have been the worst mechanism created in programming and certainly the most abused.Let the consumer code handle errors is a conceptual error and a https://pt.stackoverflow.com/q/354926/101 . It is the class of this object that should establish the rules of what is good or bad, not the consumer. Unless it's a transitional rule and it just makes sense to use there, which doesn't seem to be the case. And if it is, the second code doesn't make sense.Note that the second code, which deals with exception is not equivalent to the first since it does not treat each type of error separately. Except for being equivalent would be like this:var erros = Autenticacao.Validador(senhaNumerica); if (erros.Count == 0) return (Autenticador.Senha = true); foreach (var erro in erros) WriteLine(erro.Message); return (Autenticador.Senha = false); If you want to treat any error in a specific way it is possible to filter with the error object you have in each element of the list.Maybe you don't even need text messages, that could come within the exception itself, for me the messages there is also a mistake in most cases, but not in all.Even this code has problems. I find it weird return valueless loose, comments demonstrate that you should have a method there, mix business rule with presentation to the user.You have another problem, only one exception will be released. To indicate the 4 errors there would have to create a single exception and internalize the 4 problems and deal with them if each, the logic is even more complex, understood how it does not have to escape various checks?If the original only throws one Exception is the extreme engineering error, this information is not useful, the main reason for the exception being created is to have richer information about the error. No link above I speak of error codes showro which has better mechanism to carry rich information about error.Note that the code shown capturing exception will show that the password does not follow the rules even if the error is memory, even if it is a programming error, or something else not expected, for example database (it will one day the validator needs to access the database). That's why many programs are chaos, because "stop from day to night", people program to work, not to be right. What works one day doesn't work the other.Obviously for the code that has no exception do the same also needs 4 ifs. And the validator method would need to return an object that has the 4 invalities. Something like this:public List<ValidationError> Validador(string senha) { var erros = new List<ValidationError>(); if (!int.TryParse(SenhaNumerica, out var senhaConvertida)) erros.Add(new ValidationError(SenhaNaoNumerica, "A senha não é numérica")); if (senha.Length <= 5) erros.Add(new ValidationError(SenhaMuitoPequena, "Senha não numérica.")); if (senhaConvertida[0]) < 4) erros.Add(new ValidationError(SenhaInicioAbaixoDe4, "Não pode começar com número abaixo de 4.")); if (!senha.Any(ch => !Char.IsLetterOrDigit(ch)) erros.Add(new ValidationError(SenhaSemCaractereEspecial, "Não foi encontrado nenhum caractere especial")); return erros; } Obviously it would have to create a structure for ValidationError which would probably have these two fields (if needing more things maybe need a class, which I would avoid almost at all costs), a field to hold an object that indicates error canonically and another with the message. It's like an exception but very lightly. It could also be useful a type that loads all errors more abstractly than a list of them. Finally, I would have to create these objects indication markers of what is the error. It could be an enumeration, but isolated objects are more object-oriented.Now it can consume more or less like this:var Autenticador.Senha = SenhaNumerica; } catch (SenhaNaoNumericaException) { Console.WriteLine("A senha não é numérica"); } catch (SenhaMuitoPequenaException) { Console.WriteLine("Senha não numérica."); } catch (SenhaInicioAbaixoDe4Exception) { Console.WriteLine("Não pode começar com número abaixo de 4."); } catch (SenhaSemCaractereEspecialException) { Console.WriteLine("Não foi encontrado nenhum caractere especial"); } These codes are simplified and naive. In a real system I would give much more attention to how to do. I'd actually have so much reuse that I wouldn't even do any work. I note that much of the programmers repeat a lot of development effort, some come to do 20 times more than they could if they sought the right path.The question demonstrates a dichotomy that does not exist, is presenting codes that do very distinct things, they cannot be compared.Even the original code could be better written, for example:if (!int.TryParse(senhaNumerica, out var senhaValida)) WriteLine("A senha não é numérica"); https://github.com/maniero/SOpt/blob/master/CSharp/Exception/ManyWays.cs .Note that nomenclatures are not good for C# standards.One thing I notice here at SOpt is that developers don't create their exceptions. It's a mist of laziness with ignorance. If he does not create an exception because he does not understand, he should stay away from them at all. If you find it very laborious, you should also avoid them and adopt other solutions, you should stop capturing where you don't need it. I note that most codes could be smaller, simpler, more readable, more robust, more performable and more debugable. If programmers spent a few hours learning about exceptions in the right way would save many hours in development.Another detail that I show up as gives much more work to program object-oriented and most inexperienced programmers (qualitatively) who say program or want to program OO has no patience to deal with this work too much. I'm not going to get on the merits whether or not I'm going to that extra job, it depends on the case. The way most program, it doesn't pay off.Anyway, you can write a lot more, but it gives a chapter of a book, maybe a book just about exceptions.

Using the Library HtmlAgilityPack and using XPath to capture the div you can get the content of itHtmlAgilityPack.HtmlDocument document = new HtmlAgilityPack.HtmlDocument(); document.LoadHtml(html); HtmlAgilityPack.HtmlNode node = document.DocumentNode; HtmlAgilityPack.HtmlNode content = node.Descendants("div"). Where(div => div.GetAttributeValue("id", string.Empty) == "content"). FirstOrDefault(); See working on https://dotnetfiddle.net/EZQdYW Obs: It is necessary to install the library HtmlAgilityPack in your project via NuGet

It makes no sense that you are wanting, the finally, is for you to perform the necessary logics if the block try get or don't do your job.For exampleYou open the connection with SQL and then during a query the connection drops will be generated an exception, but giving right or error you need to close the connection with SQL, so you put this logic in the finally.If you want to skip the finally simply remove it.

What is the difference between using if and tryWell, they're very different from each other. if serves to make a conditional flow. try ... catch serves to take errors (or exceptions, in the correct language) and give these errors the proper treatment. For example, in your code:try { SalarioBase = Convert.ToDouble(textBox1.Text); Vantagens = Convert.ToDouble(textBox2.Text); Descontos = Convert.ToDouble(textBox3.Text); } catch { MessageBox("Valores inválidos"); return; } If there is a conversion error in any of the three fields, your code will go to catch, that is, you will print an error message and exit the function. About the title of your question:What most recommended try or ifThere's no such thing as "we recommend" in this case. Each serves a different purpose, so much that they can be used together. For example:try { if (!Double.TryParse(textBox1.Text, out SalarioBase)) { MessageBox("Salário não está no formato correto."); } if (!Double.TryParse(textBox2.Text, out Vantagens)) { MessageBox("Vantagens não está no formato correto."); } if (!Double.TryParse(textBox3.Text, out Descontos)) { MessageBox("Descontos não está no formato correto."); } } catch { MessageBox("Ocorreu algum erro não previsto."); return; }

To understand the block try/catch it is necessary to understand the concept of exception. Do not be frightened, it is quite common that this concept causes strangeness when you start studying the paradigm of object orientation.ExceptionIn computer science, exception is an object that defines an alternate stream to the normal execution of the program. This happens when some conditions in part of the program are not satisfied, but that can be treated, so the expression treatment of exceptions. It is widely used when developing reusable libraries, in which the implemented business logic cannot be so rigid, as it would be stuck to an application only.Imagine that you have a function that makes the square root of a number. The code would be similar to this:function sqrt ($number) { // Calcula a raiz quadrada return $result; } However, considering only real numbers, the function will only work correctly if the input parameter is a non-negative value. In this way, if the parameter is negative, you should create an alternative stream for the program through an exception.function sqrt ($number) { if ($number < 0) { throw new \Exception("$number must be a non-negative number"); } // Calcula a raiz quadrada return $result; } In this way, when trying to calculate the square root of a negative number, we would have:> sqrt(-1); Uncaught Exception: -1 must be a non-negative number ... Exception treatmentWith the block try/catch you have the freedom to decide which will be the new flow of the program. In this example, let's say that if the input value is negative, I want to calculate the square root of the same value, but positive, issuing a warning for the user. We could do something like:$value = -4; try { $result = sqrt($value); } catch (\Exception $e) { log($e->getMessage()); $value *= -1; // Inverte o valor de $value $result = sqrt($value); warning("$value era negativo, então seu sinal foi alterado"); } // Continuo com minha aplicação, onde $result = 2... Being $e an instance of Exception, the method getMessage will return the defunct error message at the time of your shot. In that case, it would be stored in log system message $number must be a non-negative number.Your exampleUsing the Library PDO for connection to the database, we can see in http://php.net/manual/pt_BR/pdo.construct.php that the class builder fires an exception of the type PDOException if the connection fails. So, doing:Collaboration http://chat.stackexchange.com/users/125288/bonifazio try{ $pdo = new PDO(...); $pdo->setAttribute(...); ... }catch(PDOException $e){ // Omite a mensagem de erro para o cliente, só informando que houve um erro interno e salva o erro no log log($e->getMessage()); http_response_code(500); die("Ooops! Algo errado não está certo. Por favor, volte mais tarde."); } You guarantee that in the line $pdo->setAtributte the variable $pdo be an instance of PDO with the active connection, therefore, if the conxon fails, the course of the program is changed to the block catch. Without the use of blocks try/catch you do not have this warranty. If the connection is not successful, the HTTP response 500 code is issued, informing an internal error, also showing the message to the user (considering that the connection to the bank is trivial for the operation of the system, which is what usually occurs).You can ask yourself: but just put one if there I get the same guarantee. You can, but imagine you're using a third-party library in your application. If such an error happens, it is not a good practice that you edit the source code directly by changing it to your application. If the library has been well done, it will trigger the exception when situations so occur and you capture them can do the treatment without changing the code.