Get error type java

Errors V/s Exceptions In Java

In Java, errors and exceptions are both types of throwable objects, but they represent different types of problems that can occur during the execution of a program.

Errors are usually caused by serious problems that are outside the control of the program, such as running out of memory or a system crash. Errors are represented by the Error class and its subclasses. Some common examples of errors in Java include:

• OutOfMemoryError: Thrown when the Java Virtual Machine (JVM) runs out of memory.
• StackOverflowError: Thrown when the call stack overflows due to too many method invocations.
• NoClassDefFoundError: Thrown when a required class cannot be found.

Since errors are generally caused by problems that cannot be recovered from, it’s usually not appropriate for a program to catch errors. Instead, the best course of action is usually to log the error and exit the program.

Exceptions, on the other hand, are used to handle errors that can be recovered from within the program. Exceptions are represented by the Exception class and its subclasses. Some common examples of exceptions in Java include:

• NullPointerException: Thrown when a null reference is accessed.
• IllegalArgumentException: Thrown when an illegal argument is passed to a method.
• IOException: Thrown when an I/O operation fails.

Since exceptions can be caught and handled within a program, it’s common to include code to catch and handle exceptions in Java programs. By handling exceptions, you can provide more informative error messages to users and prevent the program from crashing.

In summary, errors and exceptions represent different types of problems that can occur during program execution. Errors are usually caused by serious problems that cannot be recovered from, while exceptions are used to handle recoverable errors within a program.

In java, both Errors and Exceptions are the subclasses of java.lang.Throwable class. Error refers to an illegal operation performed by the user which results in the abnormal working of the program. Programming errors often remain undetected until the program is compiled or executed. Some of the errors inhibit the program from getting compiled or executed. Thus errors should be removed before compiling and executing. It is of three types:

Whereas exceptions in java refer to an unwanted or unexpected event, which occurs during the execution of a program i.e at run time, that disrupts the normal flow of the program’s instructions.

Now let us discuss various types of errors in order to get a better understanding over arrays. As discussed in the header an error indicates serious problems that a reasonable application should not try to catch. Errors are conditions that cannot get recovered by any handling techniques. It surely causes termination of the program abnormally. Errors belong to unchecked type and mostly occur at runtime. Some of the examples of errors are Out of memory errors or System crash errors.

Example 1 Run-time Error

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How to check which exception type was thrown in Java?

How can I determine which type of exception was caught, if an operation catches multiple exceptions? This example should make more sense:

try < int x = doSomething(); >catch (NotAnInt | ParseError e) < if (/* thrown error is NotAnInt */) < // line 5 // printSomething >else < // print something else >> 

On line 5, how can I check which exception was caught? I tried if (e.equals(NotAnInt.class)) <..>but no luck. NOTE: NotAnInt and ParseError are classes in my project that extend Exception .

4 Answers 4

If you can, always use separate catch blocks for individual exception types, there’s no excuse to do otherwise:

> catch (NotAnInt e) < // handling for NotAnInt >catch (ParseError e) < // handling for ParseError >

. unless you need to share some steps in common and want to avoid additional methods for reasons of conciseness:

> catch (NotAnInt | ParseError e) < // a step or two in common to both cases if (e instanceof NotAnInt) < // handling for NotAnInt >else < // handling for ParseError >// potentially another step or two in common to both cases > 

however the steps in common could also be extracted to methods to avoid that if — else block:

> catch (NotAnInt e) < inCommon1(e); // handling for NotAnInt inCommon2(e); >catch (ParseError e) < inCommon1(e); // handling for ParseError inCommon2(e); >private void inCommon1(e) < // several steps // common to // both cases >private void inCommon2(e) < // several steps // common to // both cases >

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Proper way to get error message and code from exception

Is this optimal or is there a better solution?
Also this is still unable to handle the exception in case there is no error code
(should return NO_ERROR_CODE).
How can I archive that?

Are those exceptions defined by you? If they are you can make a custom base exception with all the fields you need, catch them instead of Exception and expose those fields instead of trying to parse the message.

those exception are not defined by me. I want to read the error Code, if it comes, and then send to 3rd party by a defined error Category which i put in the value pair of HashMap. If the error Code doesn’t come, some other way to read the message and then categorize it and then again send to 3rd party. What can be a good design to do it?

2 Answers 2

In real life there are two audiences:

• the log handler with a configurable log level (ERROR) and logging (in English) with much info;
• the end user with an localized translated message, also with parameters.

The first property is that you probably want a message as format String with Object. parameters. Probably should use MessageFormat .

Sensible would be to support typed parameters.

/** Type-checkable Message Definition. */ public record MessageDef(String format, Class. parameterTypes) < public void checkFormat() < . check actual parameters with parameterTypes.length >public void checkUsage(Object[] args) < . check parameter types >> 

One could make an enum for the error categories. However enums are more suitable for closed domains with a fixed set of values. Extending values in future means that you have created a needless common bottleneck for source version control and so on. An error is more like an open domain. However if you number them with error codes, an enum gives a nice overview.

The only advantage of error codes is the internationalisation. An Hungarian error message can be easily retrieved.

Then, if you rethrow check exceptions as RuntimeException, like IllegalArgumentException or you own custom ones, you might not want parallel classes: run-time exceptions and categories.

All-in-all I would advise an enum:

public enum MessageType < INVALID_TEMPLATE(400, Level.ERROR, new MessageDef("You have got the error in .", String.class)), . REQUEST_REJECTED(200, Level.INFO, new MessageDef("Done.")); public final int code; public final Level level; public final MessageDef def; MessageType(int code, Level level, MessageDef def) < this.code = code; this.level = level; this.def = def; >> 

One small remark: such little discussion points in the beginning of a project sometimes might be better postponed to a fast refactoring after having written sufficient code. Here an enum might not fit, you might have much re-throwing of exceptions. A premature decision is not needed. And might hamper fast productivity. Especially as you probably need not mark the code places, you most likely call the same show-error dialog.

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Java exception handling get console error message

I want to get error message using java when exception are generated. now I have java code with following scenario:

method first()< try< second(); >catch(Exception e) < System.out.println("Error:>"+e) > > 

method second()< try< my code >catch(Exception e) < throw new Exception("Exception generate in second method",e); >> 

now when the first method execute then I get only «Exception generate in second method» message but there is some other message printed on console by java so how to get that console error message. Note: I have already try with e.getMessage(); and e.printStackTrace();

Here you are getting «Exception generate in second method» only because you are catching exception in second() method and hence catch block in first() method will never be executed.

@ShoaibChikate The catch block in the second method throws an exception so it will be propagated to the calling method i;e first method. Ideally the catch block of the first method should run

5 Answers 5

Every exception has a cause that you can get with getCause() . You can go recursively down them until you get to the root cause. Here is your example with a utility that dumps the exception with all its causes like the console does.

private void first() < try < second(); >catch (Exception ex) < Log.e("CATCH", getExceptionDump(ex)); >> private void second() < try < throw new UnsupportedOperationException("We don't do this."); >catch (Exception ex) < throw new RuntimeException("Exception in second()", ex); >> private String getExceptionDump(Exception ex) < StringBuilder result = new StringBuilder(); for (Throwable cause = ex; cause != null; cause = cause.getCause()) < if (result.length() >0) result.append("Caused by: "); result.append(cause.getClass().getName()); result.append(": "); result.append(cause.getMessage()); result.append("\n"); for (StackTraceElement element: cause.getStackTrace()) < result.append("\tat "); result.append(element.getMethodName()); result.append("("); result.append(element.getFileName()); result.append(":"); result.append(element.getLineNumber()); result.append(")\n"); >> return result.toString(); > 

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Class 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. That is, Error and its subclasses are regarded as unchecked exceptions for the purposes of compile-time checking of exceptions.

Constructor Summary

Constructs a new error with the specified detail message, cause, suppression enabled or disabled, and writable stack trace enabled or disabled.

Constructs a new error with the specified cause and a detail message of (cause==null ? null : cause.toString()) (which typically contains the class and detail message of cause ).

Method Summary

Methods declared in class java.lang.Throwable

Methods declared in class java.lang.Object

Constructor Details

Error

Constructs a new error with null as its detail message. The cause is not initialized, and may subsequently be initialized by a call to Throwable.initCause(java.lang.Throwable) .

Error

Constructs a new error with the specified detail message. The cause is not initialized, and may subsequently be initialized by a call to Throwable.initCause(java.lang.Throwable) .

Error

Constructs a new error with the specified detail message and cause. Note that the detail message associated with cause is not automatically incorporated in this error’s detail message.

Error

Constructs a new error with the specified cause and a detail message of (cause==null ? null : cause.toString()) (which typically contains the class and detail message of cause ). This constructor is useful for errors that are little more than wrappers for other throwables.

Error

protected Error (String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace)

Constructs a new error with the specified detail message, cause, suppression enabled or disabled, and writable stack trace enabled or disabled.

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