Error meaning in java

difference between errors and unchecked exceptions in java?

As we know if any error or any unchecked exception occurs then our program will halt, then what are the differences between those?

7 Answers 7

You can, and probably should, recover from an exception.

You can, but should not, recover from an error.

@Eric Eijkelenboom: Maybe you meant «you should not recover from an error»? Because Error extends Throwable and any Throwable is surely easy to catch and a great many Error can be recovered from (OutOfMemoryError, just to name one, is quite easy to work around in applications that have big caches that can be discarded at will).

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.

The class Exception and its subclasses are a form of Throwable that indicates conditions that a reasonable application might want to catch.

So, even though an unchecked exception is not required to be caught, you may want to. An error, you don’t want to catch.

Unchecked Exception:

• The classes that extend RuntimeException are 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 exception they are caused by faults in code flow or configuration.
• Example: ArithmeticException , NullPointerException , ArrayIndexOutOfBoundsException etc
• 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 NullPointerException by simply checking the references — if(object!=null) or using even better techniques

• Error refers irrecoverable situation that are not being handled by try/catch
• Example: OutOfMemoryError , VirtualMachineError , AssertionError etc. This question may also be helpful in this context — Runtime/Checked/Unchecked/Error-Exception

An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch.

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

So, the only difference technically is that they are two different classes. You will only catch both if you declare

But there is a big difference in how they are intended to be used. Unchecked exceptions ( RuntimeExceptions ) are intended to deal with programming errors and other unexpected problems, but should be caught and handled in the application. Errors are intended to represent problems that the program cannot deal with, such as running out of memory.

Just as checked exceptions are useful for signaling when your methods cannot fulfill their contract, there are other errors outside of your control that can occur that prevent the Java virtual machine from fulfilling its specification, such as when memory is exhausted. Since you can’t plan for such errors ahead of time, you would have to catch them everywhere, which defeats the principle of maintaining uncluttered code. Therefore, these errors are unchecked exceptions, meaning exceptions that you don’t have to include in a throws clause. You are welcome to catch them (well, some of them), but the compiler won’t make you do it. Unchecked exceptions fall into two categories: those that extend RuntimeException, and those that extend Error. I realize that I said earlier that classes inheriting from class Exception are checked exceptions, but that’s only half true: the whole truth is that classes in the Exception hierarchy other than those in the RuntimeException sub-hierarchy are checked exceptions.

Exceptions that extend RuntimeException represent errors that you may want to handle, although you’re not required to.

As I stated above, RuntimeExceptions are not checked because making you advertise them would have no effect on establishing the correctness of your methods, and would unnecessarily clutter your otherwise very readable code. Exceptions derived from the Error class, on the other hand, are unchecked because you never want to catch them! Error exceptions are severe errors that require shutting down the virtual machine. InternalError, which I used above, extends VirtualMachineError, which is an Error subclass. OutOfMemoryError is another obvious severe error, but there are others, like StackOverflowError, and various LinkageErrors. A linkage error means something has gone amiss when the class loader tried to load a class for execution, and commonly occurs either because some external source has introduced malicious code in an attempt to circumvent Java’s security mechanism, or it came from an out-of-spec byte code generator.

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Error meaning in java

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 Detail

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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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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Error meaning in java

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