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What is Exception? Dictionary Meaning: Exception is an abnormal condition. In java, exception is an event that disrupts the normal flow of the program. It is an object which is thrown at runtime. Types of Exception There are mainly two types of exceptions: checked and unchecked where error is considered as unchecked exception. The sun microsystem says there are three types of exceptions: 1)Checked Exception 2)Unchecked Exception 3)Error Difference between checked and unchecked exceptions 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.

What is marker or tagged interface? An interface that have no member is known as marker or tagged interface. For example: Serializable, Cloneable, Remote etc. They are used to provide some essential information to the JVM so that JVM may perform some useful operation. //How Serializable interface is written? public interface Serializable{ }  

Found this interesting.Courtesy-StackOverFlow This is just convention. In fact, even the name main(), and the arguments passed in are purely convention. When you run java.exe (or javaw.exe on Windows), what is really happening is a couple of Java Native Interface (JNI) calls. These calls load the DLL that is really the JVM (that's right - java.exe is NOT the JVM). JNI is the tool that we use when we have to bridge between the virtual machine world, and the world of C, C++, etc... The reverse is also true - it is not possible (at least to my knowledge) to actually get a JVM running without using JNI. Basically, java.exe is a super simple C application that parses the command line, creates a new String array in the JVM to hold those arguments, parses out the class name that you specified as containing main(), uses JNI calls to find the main() method itself, then invokes the main() method, passing in the newly created string array as a parameter. This is very, very much like w