Exception handling syntax: Difference between revisions

Revision as of 06:10, 20 January 2025

Latest revision as of 23:17, 3 July 2025

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{{Further|C++}}

<syntaxhighlight lang="cpp">

import std;

#include <exception>

int main() {

try {

// do something (might throw an exception)

} catch (const std::exception&runtime_error e) {

}

// handle a runtime_error e

catch (const std::exception& e) {

} catch (const // handle std::exception& e) {

// catches all exceptions as e

}

} catch (...) {

// catches all exceptionsthrown types (including primitives or objects that do nit extend exception), not already caught by a catch block before

}

// can be used to catch exception of unknown or irrelevant type

}

}

</syntaxhighlight>

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try {

// code which could result in an exception

} catch (any e){

retry;

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<syntaxhighlight lang="cpp">

import std;

#include <iostream>

using namespace std;

int main() {

try {

{

throw static_cast<int>(42);

try

{throw} catch(intdouble e)42;} {

std::println("(0,{})", e);

catch(double e)

{cout} << "catch(0," <<int e << ")" << endl;}{

std::println("(1,{})", e);

catch(int e)

}

{cout << "(1," << e << ")" << endl;}

}

</syntaxhighlight>

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}

</syntaxhighlight>

If multiple resources are acquired, the correct way to deal with them is with nested try blocks.<ref>Bloch, Joshua (2018). ''Effective Java, Third Edition''. Addison-Wesley. Item 9, p. 54. {{ISBN|978-0-13-468599-1}}</ref> For this reason and others, ''try-with-resources'' was added to the language to almost entirely replace finally clauses. Resources acquired in a parentheses after the try keyword will be cleaned up automatically. Classes used in these statements must implement an interface called AutoCloseable.<ref>{{cite web | url=https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html | title=The try-with-resources Statement (The Java™ Tutorials > Essential Java Classes > Exceptions) }}</ref>

<syntaxhighlight lang="java">

try (FileReader fr = new FileReader(path);

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} catch (IOException ioe) {

// Deal with exception.

} // File and streamResources in the try statement are automatically closed afterwards.

finally {

// A finally blockclause can be included here as well, and will run after the resources in the try statements are closed.

}

</syntaxhighlight>

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// Statements in which exceptions might be thrown

throw new Error("error");

} catch (error) {

// Statements that execute in the event of an exception

} finally {

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try {

throw 12345; // primitive number

} catch (error) {

console.log(error); // logs 12345 as a primitive number to the console

}

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// Example in Java

try {

Integer i = null;

i.intValue(); // throws a NullPointerException

} catch (NullPointerException error) {

// Variable might be null

} catch (ArithmeticException error) {

// Handle problems with numbers

}

</syntaxhighlight>

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var example = null;

example.toString();

} catch (error) {

if (error.type === "TypeError") {

// Variable might be null

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var example = null;

example.toString();

} catch (error) {

if (error.type !== "TypeError") throw error;

// Variable might be null

}

} catch (error) {

if (error.type !== "RangeError") throw error;

// Handle problems with numbers

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obj.selfPropExample = obj; // circular reference

throw obj;

} catch (error) {

// Statements that execute in the event of an exception

}

</syntaxhighlight>

=== Kotlin ===

{{Further|Kotlin (programming language)}}

<syntaxhighlight lang="kotlin">

try {

// Code that may throw an exception

} catch (e: SomeException) {

// Code for handling the exception

}

</syntaxhighlight>