Question

Every program I run in java gives similiar error.

This is a helloworld program:

Exception in thread "main" java.lang.NoClassDefFoundError: helloworld (wrong nam
e: helloworldapp)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(Unknown Source)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: helloworld.  Program will exit.

Answer 1

Try this one:

public class HelloWorld 
{
  public static void main(String[] args) 
  {
    System.out.println("Hello World!");
  }
}

Read this tutorial about this problem.