What is classNotFound Exception in java?

Answer 1

If you are getting this error message, it means you are trying to use a class that is not located in your JVM classpath. In order to resolve this error, you must find the .class or the .jar file that contains the class you need, and add it to your classpath.

Depending on the application, it might be as simple as changing your CLASSPATH environment variable. Here is a good article on the Java classpath:

http://en.wikipedia.org/wiki/Classpath_(Java)

Here is a good online utility to help you quickly find the right jar and download it. It will save you hours of searching through various blog posts on the internet trying to find out which jar contains which class file!

http://www.ClassNotFound.com/

Answer 2

A classnotfound exception is usually thrown when the JVM cannot locate a particular class.

This usually happens when you are referring to java classes available inside jars. you would have included your jar in the project's build path hence there would be no compile time errors. But when you execute your app, you would've missed to add that jar into the server path. Hence the server is unable to locate the jar and the JVM would throw this exception.

Answer 3

A class cast exception is thrown by Java when you try to cast an Object of one data type to another.

Java allows us to cast variables of one type to another as long as the casting happens between compatible data types.

For example you can cast a String as an Object and similarly an Object that contains String values can be cast to a String.

Example:

Let us assume we have an HashMap that holds a number of ArrayList objects.

if we write a code like this:

String obj = (String) hmp.get(key);

it would throw a class cast exception because the value returned by the get method of the hash map would be an Array list but we are trying to cast it to a String. This would cause the exception.

Answer 4

A ClassNotFoundException normally occurs when you try to run a Java program, but Java can't find your main class. The fix to this problem is to use the -cp command-line flag to set the Java classpath and tell it where your .class files are.

Answer 5

You can find information on java lang class not found on many blogs. You can also find information on Stackoverflow and Revisited. This relates to the Java Platform.