What are the different types of Exceptions in Java?

Exception is an abnormal condition or error that arises during an application processing at run time. The parent class is the Throwable class which has two direct subclasses, java.lang.Error and java.lang.Exception. custom exception that extends the Exception class. The JVM takes care of throwing an instance of Error object when there is a system error. The proper Exception handling useful in tracking and debugging errors in the application and sub systems. All the exceptions, which are caught and handled within the calling method or declared in the throws clause of the method, are categorized under checked exceptions. All the checked exceptions must be a sub class of java.lang. Exception class. The JVM will verify that all the checked exceptions are taken care properly by the calling method in the class. Unchecked Exceptions The exception which are raised because of incorrect logic or programming errors are categorized as Unchecked exceptions. These exceptions are sub classes of RunTimeException class. The JVM will not verify for these exceptions in the calling method read less

1) Checked Exception The classes that extend Throwable class except RuntimeException and Error are known as checked exceptions e.g.IOException, SQLException etc. Checked exceptions are checked at compile-time. 2) Unchecked Exception The classes that extend RuntimeException are known as unchecked exceptions e.g. ArithmeticException, NullPointerException, ArrayIndexOutOfBoundsException etc. Unchecked exceptions are not checked at compile-time rather they are checked at runtime. 3) Error Error is irrecoverable e.g. OutOfMemoryError, VirtualMachineError, AssertionError etc. read less

An exception (or exceptional event) is a problem that arises during the execution of a program. When an Exception occurs the normal flow of the program is disrupted and the program/Application terminates abnormally, which is not recommended, therefore these exceptions are to be handled. An exception can occur for many different reasons, below given are some scenarios where exception occurs. A user has entered invalid data. A file that needs to be opened cannot be found. A network connection has been lost in the middle of communications or the JVM has run out of memory. Some of these exceptions are caused by user error, others by programmer error, and others by physical resources that have failed in some manner. Based on these we have three categories of Exceptions you need to understand them to know how exception handling works in Java, Checked exceptions: A checked exception is an exception that occurs at the compile time, these are also called as compile time exceptions. These exceptions cannot simply be ignored at the time of compilation, the Programmer should take care of (handle) these exceptions. For example, if you use FileReader class in your program to read data from a file, if the file specified in its constructor doesn't exist, then an FileNotFoundException occurs, and compiler prompts the programmer to handle the exception. import java.io.File; import java.io.FileReader; public class FilenotFound_Demo { public static void main(String args[]){ File file=new File("E://file.txt"); FileReader fr=new FileReader(file); } } If you try to compile the above program you will get exceptions as shown below. C:\>javac FilenotFound_Demo.java FilenotFound_Demo.java:8: error: unreported exception FileNotFoundException; must be caught or declared to be thrown FileReader fr = new FileReader(file); ^ 1 error Note: Since the methods read() and close() of FileReader class throws IOException, you can observe that compiler notifies to handle IOException, along with FileNotFoundException. Unchecked exceptions: An Unchecked exception is an exception that occurs at the time of execution, these are also called as Runtime Exceptions, these include programming bugs, such as logic errors or improper use of an API. runtime exceptions are ignored at the time of compilation. For example, if you have declared an array of size 5 in your program, and trying to call the 6th element of the array then an ArrayIndexOutOfBoundsExceptionexception occurs. public class Unchecked_Demo { public static void main(String args[]){ int num[]={1,2,3,4}; System.out.println(num[5]); } } If you compile and execute the above program you will get exception as shown below. Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5 at Exceptions.Unchecked_Demo.main(Unchecked_Demo.java:8) Errors: These are not exceptions at all, but problems that arise beyond the control of the user or the programmer. Errors are typically ignored in your code because you can rarely do anything about an error. For example, if a stack overflow occurs, an error will arise. They are also ignored at the time of compilation. read less

Exceptions are 2 types. 1.Checked 2.Uncheked All the exception for that compiler doesn't care are comes under unchecked exception i.e. ArithmaticException, ArrayIndexOutofBoundexp etc Exceptions which needs to be defined in throws clause of a method r checked exception,ie.sevletException,ClassNotFoundExp,NoSuchFieldException etc read less