Checked and Unchecked Exceptions in Java


Exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program's instructions. By using try-catch in a method and if any error occurs then object creates and handed over to the run-time system. Those objects are called as Exception object which contains information's about the exception occurred. 
In our earlier tutorial we have seen difference between throw and throws in java and these exception objects are called as throwing an exception to the run-time system. Normally there are 3 types of Exceptions in Java and they are 

1. Checked exception (or) Compile time exception 
2. Unchecked exception (or) Run-time exception
3. Error 

Below are the Exception hierarchy in Java.


Checked and Unchecked Exceptions in Java


Checked Exception:

Exceptions which are checked under the block or method and caught at compile time are called as checked exceptions. For example if we are reading a file with input as file name and by mistake file name supplied with wrong name then FileNotFoundException will be thrown from the constructor for non-existing file. A well written program will catch those exception and passed to the run-time system. 

Unchecked Exception:

Unchecked Exception are also called as run-time exception which are exceptional conditions that are internal to the application, and that the application usually cannot anticipate or recover from. These are usually called as programming bugs are API errors which occurs at run-time. For example consider a method passes the file-name to other method. By some programming flaws its started sending null to the method which caught under NullPointerExpcetion.

Errors: 

Errors also called as unchecked exceptions which are exceptional conditions that are internal to the application, and that the application usually cannot anticipate or recover from. For example if application successfully opens a input file, but is unable to read the file because of a hardware or system failure are called as Errors which can't be recovered. 

Below are the few list of checked and Unchecked exceptions in java 

Checked Exceptions:

Exception
FileNotFoundException
ParseException
IOException
NoSuchFieldException
NoSuchMethodException
ClassNotFoundException
CloneNotSupportedException
InstantiationException
InterruptedException


Unchecked Exceptions:

NullPointerException
NumberFormatException
ArrayIndexOutOfBoundsException
AssertionError
NoClassDefFoundError
ClassCastException
StackOverflowError
IllegalArgumentException
IllegalStateException
ExceptionInInitializerError


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