Java Exceptions HandlingSelasa, 2008-11-04, 16:50:27
Oleh : Administrator
 Exceptions in java are any abnormal, unexpected events or extraordinary conditions that may occur at runtime. They could be file not found exception, unable to get connection exception and so on. On such conditions java throws an exception object. Java Exceptions are basically Java objects. No Project can never escape a java error exception.
Java exception handling is used to handle error conditions in a program systematically by taking the necessary action. Exception handlers can be written to catch a specific exception such as Number Format exception, or an entire group of exceptions by using a generic exception handlers. Any exceptions not specifically handled within a Java program are caught by the Java run time environment
An exception is a subclass of the Exception/Error class, both of which are subclasses of the Throwable class. Java exceptions are raised with the throw keyword and handled within a catch block.
Example : A Program Showing How the JVM throws an Exception at runtime
public class DivideException
{
public static void main(String[] args)
{
division(100,4); // Line 1
division(100,0); // Line 2
System.out.println("Exit main().");
}
public static void division(int totalSum,
int totalNumber)
{
System.out.println("Computing Division.");
int average = totalSum/totalNumber;
System.out.println("Average : "+ average);
}
}
Output
Computing Division.
Average : 25
Computing Division.
Exception in thread "main" java.lang.ArithmeticException:/by zero
at DivideException.division(DivideException.java:11)
at DivideException.main(DivideException.java:5)
Exceptions in Java
Throwable Class
The Throwable class provides a String variable that can be set by the subclasses to provide a detail message that provides more information of the exception occurred. All classes of throwables define a one-parameter constructor that takes a string as the detail message.
The class Throwable provides getMessage() function to retrieve an exception. It has a printStackTrace() method to print the stack trace to the standard error stream. Lastly It also has a toString() method to print a short description of the exception. For more information on what is printed when the following messages are invoked, please refer the java docs.
Syntax
String getMessage()
void printStackTrace()
String toString()
Class Exception
The class Exception represents exceptions that a program faces due to abnormal or special conditions during execution. Exceptions can be of 2 types: Checked (Compile time Exceptions)/ Unchecked (Run time Exceptions).
Class RuntimeException
Runtime exceptions represent programming errors that manifest at runtime. For example ArrayIndexOutOfBounds, NullPointerException and so on are all subclasses of the java.lang.RuntimeException class, which is a subclass of the Exception class. These are basically business logic programming errors.
Class Error
Errors are irrecoverable condtions that can never be caught. Example: Memory leak, LinkageError etc. Errors are direct subclass of Throwable class. |
