Code for Exception in Java

[taher]

Can someone help me to write a code for an exception in Java. No problem if there is no detailed coding about the exception, just few lines will be OK, so I can understand the logic of it. Lets assume that I have got my main function. In that I am asking the user to input their First Name. Now I want an exception saying that "You have to enter the name" or "You have entered a number as your name, type properly" when the user has entered nothing or the user has entered the number in the Name field. Also can I handle the exceptions in the other class.?? So that it gets triggered when such scene occurs. Can someone help me..??

[kelfro]

The event that occurs during the execution of a program, which disrupts the normal flow of the program's instructions is known as an Exception. The method creates an object and hands it off to the runtime system when an error occurs within a method. The object that contains information about the error, including its type and the state of the program when the error occurred is called as exception object. Handling an exception to the runtime system is called as throwing an exception.

[Zecho]

If the Java program is valid then it should honor the Catch or Specify Requirement. Then only it can called as Valid Java programming language's code. The exceptions must be enclosed by either of the following if the code that might throw :
A try statement that catches the exception.

• As described in Catching and Handling Exceptions, the try must provide a handler for the exception.
• A method that specifies that it can throw the exception. Also as described in Specifying the Exceptions Thrown by a Method, the method must provide a throws clause that lists the exception.

[Praetor]

Here is an example of the exception :

while (noError == false)
{
try{
System.out.println (" Please enter your name : " );
int x = keyboard.nextInt();
if ( (string !==null))
{
throw new java.lang.Exception();
}
else
{
noError = true;
}
}

catch (InputMismatchException exception)
{
System.err.println (" Wrong input ! Please input characters only !");
}
catch (java.lang.Exception ee)
{
System.err.println ( " Please enter a valid name, check your name ! " );
}
}

This program will ask the user to enter a name and throws an exception if the user enters the numeric to name field.

[Modifier]

I am giving an example of throw statement in context. The method removes the top element from the stack and returns the object. The following pop method is taken from a class that implements a common stack object :

public Object pop() {
Object obj;

if (size == 0) {
throw new EmptyStackException();
}
obj = objectAt(size - 1);
setObjectAt(size - 1, null);
size--;
return obj;
}