Java 未检查异常或运行时异常之间的区别

Difference between Unchecked exception or runtime exception

提问by giri

This was an interview question. What is the main difference between unchecked exception and error as both are not caught? They will terminate the program.

这是一道面试题。未经检查的异常和错误之间的主要区别是什么，因为两者都没有被捕获？他们将终止该计划。

回答by matt b

The JavaDocs sum these up pretty well.

JavaDocs 很好地总结了这些。

java.lang.RuntimeException:

java.lang.RuntimeException：

RuntimeException is the superclass of those exceptions that can be thrown during the normal operation of the Java Virtual Machine.

A method is not required to declare in its throws clause any subclasses of RuntimeException that might be thrown during the execution of the method but not caught.

RuntimeException 是那些在 Java 虚拟机正常运行期间可以抛出的异常的超类。

方法不需要在它的 throws 子句中声明在方法执行期间可能抛出但未被捕获的 RuntimeException 的任何子类。

java.lang.Error:

java.lang.Error：

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch. Most such errors are abnormal conditions. The ThreadDeath error, though a "normal" condition, is also a subclass of Error because most applications should not try to catch it.

A method is not required to declare in its throws clause any subclasses of Error that might be thrown during the execution of the method but not caught, since these errors are abnormal conditions that should never occur.

Error 是 Throwable 的一个子类，它指示合理的应用程序不应尝试捕获的严重问题。大多数此类错误是异常情况。ThreadDeath 错误虽然是“正常”情况，但也是 Error 的一个子类，因为大多数应用程序不应该尝试捕获它。

一个方法不需要在它的 throws 子句中声明在方法执行期间可能抛出但没有被捕获的 Error 的任何子类，因为这些错误是不应该发生的异常情况。

Note that "unchecked exception" is merely a synonym for a RuntimeException.

请注意，“未经检查的异常”只是 a 的同义词RuntimeException。

回答by stacker

RuntimeExceptionsand Errors like OutOfMemoryErrordon't need to be catched and can be thrown until they reach main() which will terminate the application.

RuntimeExceptions和错误OutOfMemoryError不需要被捕获并且可以被抛出，直到它们到达将终止应用程序的 main() 。

Other Exceptions cause an compile error if they are not catched or included in the throws list.

如果其他异常未被捕获或包含在 throws 列表中，则会导致编译错误。

回答by DaveJohnston

Note: a RuntimeException IS an unchecked exception

注意：RuntimeException 是未经检查的异常

An unchecked exception would be one that is known to be possible at a point in the execution but is not caught, for example a NullPointerException is always a possibility if you don't check for them and will cause your program to terminate. You could check for it by wrapping code in try-catch, but this is not enforced (unlike a checked exception that will enforce that the exception is handled in some way).

未经检查的异常是已知在执行中的某个点可能发生但未被捕获的异常，例如，如果您不检查它们，NullPointerException 总是可能的，并且会导致您的程序终止。您可以通过在 try-catch 中包装代码来检查它，但这不是强制执行的（与强制以某种方式处理异常的已检查异常不同）。

An error is something that can occur at any point during execution and can't really be caught because it is not eplicitly caused by a particular method call etc. For example an OutOfMemoryError or a StackOverflowError. Both of these could occur at any time and will cause your application to terminate. Catching these errors make no sense as they indicate that something has happened that you won't be able to recover from.

错误是在执行过程中的任何时候都可能发生的事情，并且不能真正被捕获，因为它不是由特定方法调用等引起的。例如 OutOfMemoryError 或 StackOverflowError。这两种情况都可能随时发生，并会导致您的应用程序终止。捕捉这些错误毫无意义，因为它们表明发生了一些您无法恢复的事情。

回答by user306708

Errorsindicate fundamental problems that should never occur. If you run into an error s.th. really bad happened.
Unchecked Exceptions(Runtime Exceptions) on the other hand are used whenever an exception could be expected somehow but there is no reasonable way to deal with it then and thus a try catch statement would be just annoying and a waste of space.

错误表明根本不应该发生的问题。如果您遇到错误 s.th. 真的很糟糕发生了。另一方面，只要以某种方式可以预期异常，就会使用
未经检查的异常（运行时异常），但没有合理的方法来处理它，因此 try catch 语句只会令人讨厌并浪费空间。

回答by Pascal Thivent

As stated by their name, unchecked exceptionsare not checked at compile-timewhich means that the compiler doesn't require methods to catch or to specify (with a throws) them. Classes belonging to this category are detailed in the section 11.2 Compile-Time Checking of Exceptionsof the JLS:

正如他们的名字说，检查异常是不是在编译时检查，这意味着编译器不要求的方法来捕捉或指定（有throws）他们。属于此类别的类在第11.2节编译时检查JLS的异常中有详细说明：

The unchecked exceptions classesare the class RuntimeExceptionand its subclasses, and the class Errorand its subclasses. All other exception classes are checked exception classes. The Java API defines a number of exception classes, both checked and unchecked. Additional exception classes, both checked and unchecked, may be declared by programmers. See §11.5for a description of the exception class hierarchy and some of the exception classes defined by the Java API and Java virtual machine.

该unchecked异常类是类RuntimeException和它的子类，类Error和它的子类。所有其他异常类都是检查异常类。Java API 定义了许多异常类，包括检查的和未检查的。程序员可以声明额外的异常类，包括检查的和未检查的。有关异常类层次结构和一些由 Java API 和 Java 虚拟机定义的异常类的说明，请参见第11.5 节。

The following picture illustrates the Exception hierarchy:

下图说明了异常层次结构：

The class Errorand its subclasses are exceptions from which ordinary programs are not ordinarily expected to recover and, as explained in 11.5 The Exception Hierarchy:

类Error及其子类是普通程序通常不会从中恢复的异常，如11.5 The Exception Hierarchy 中所述：

The class Erroris a separate subclass of Throwable, distinct from Exceptionin the class hierarchy, to allow programs to use the idiom:

} catch (Exception e) {

to catch all exceptions from which recovery may be possible without catching errors from which recovery is typically not possible.

该类Error是 的一个单独子类Throwable， Exception与类层次结构不同，以允许程序使用习语：

} catch (Exception e) {

捕获可以恢复的所有异常，而不捕获通常无法恢复的错误。

To summarize, RuntimeExceptionare a subset of unchecked exceptionsfor exceptions from which recovery is possible (but unchecked exception is not a synonym of RuntimeExceptionas many are answering here).

总而言之，是可以从中恢复的异常RuntimeException的未经检查的异常的子集（但未经检查的异常并不是RuntimeException许多在这里回答的同义词）。

回答by grepit

Errors and runtime exceptions are collectively known as unchecked exceptions.

错误和运行时异常统称为未检查异常。

runtime exceptions are exceptional conditions that are internal to the application, and that the application usually cannot anticipate or recover from. These usually indicate programming bugs, such as logic errors or improper use of an API

运行时异常是应用程序内部的异常情况，应用程序通常无法预测或从中恢复。这些通常表示编程错误，例如逻辑错误或 API 使用不当

You may want to take a look at this link which explains the Three Kinds of Exceptions.

您可能想看看这个链接，它解释了三种异常。

http://docs.oracle.com/javase/tutorial/essential/exceptions/catchOrDeclare.html

http://docs.oracle.com/javase/tutorial/essential/exceptions/catchOrDeclare.html

I hope this helps.

我希望这有帮助。

回答by Vineeta Khatuja

Error: These are exceptional conditions that are externalto the application, and that the application usually cannot anticipate or recover from.

错误：这些是应用程序外部的异常情况，应用程序通常无法预测或从中恢复。

Runtime exception: These are exceptional conditions that are internalto the application, and that the application usually cannot anticipate or recover from.

运行时异常：这些是应用程序内部的异常情况，应用程序通常无法预测或从中恢复。

You may want to read this:

您可能想阅读以下内容：

回答by Razib

Checked Exception:

检查异常：

• The classes that extend Throwableclass except RuntimeExceptionand Errorare known as checked exceptions.
• Also known as compile time exception because these type of exceptions are checked at compile time. That means if we ignore these exception (not handled with try/catchor throwthe exception) then a compilation error occurred.
• They are programmatically recoverable problems which are caused by unexpected conditions outside control of code (e.g. database down, file I/O error, wrong input, etc)
• We can avoid them using try/catchblock.
• Example:IOException, SQLExceptionetc

• 扩展的类Throwable类，除了RuntimeException和Error被称为checked异常。
• 也称为编译时异常，因为这些类型的异常是在编译时检查的。这意味着如果我们忽略这些异常（未处理try/catch或throw异常），则会发生编译错误。
• 它们是由代码控制之外的意外情况（例如数据库关闭、文件 I/O 错误、错误输入等）引起的可通过编程方式恢复的问题
• 我们可以使用try/catch块来避免它们。
• 例如：IOException，SQLException等

Unchecked Exception:

未经检查的异常：

• The classes that extend RuntimeExceptionare known as unchecked exceptions
• Unchecked exceptions are not checked at compile-time rather they are checked at runtime.And thats why they are also called "Runtime Exception"
• They are also programmatically recoverable problems but unlike checked exceptionthey are caused by faults in code flow or configuration.
• Example:ArithmeticException,NullPointerException, ArrayIndexOutOfBoundsExceptionetc
• Since they are programming error, they can be avoided by nicely/wisely coding. For example "dividing by zero" occurs ArithmeticEceeption. We can avoid them by a simple if condition - if(divisor!=0). Similarly we can avoid NullPointerExceptionby simply checking the references - if(object!=null)or using even better techniques

• 扩展的类RuntimeException称为未经检查的异常
• 未经检查的异常不在编译时检查，而是在运行时检查。这就是为什么它们也被称为“运行时异常”
• 它们也是可通过编程方式恢复的问题，但与检查异常不同，它们是由代码流或配置中的错误引起的。
• 例如：ArithmeticException，NullPointerException，ArrayIndexOutOfBoundsException等
• 由于它们是编程错误，因此可以通过良好/明智的编码来避免它们。例如，发生“除以零” ArithmeticEceeption。我们可以通过一个简单的 if 条件来避免它们 - if(divisor!=0)。同样，我们可以NullPointerException通过简单地检查引用来避免-if(object!=null)或者使用更好的技术

Error:

错误：

• Errorrefers irrecoverable situation that are not being handled by try/catch
• Example:OutOfMemoryError, VirtualMachineError, AssertionErroretc.

• Error指的是 try/catch 没有处理的不可恢复的情况
• 例如：OutOfMemoryError，VirtualMachineError，AssertionError等。