Do you get the following error message?
Exception in thread "main" java.lang.NoSuchMethodError: main
If so, the following are common causes.
mainheader. Something is wrong with your declaration of
main. It must be
public static void main(String args)Slight variations in the parameter declaration are allowed, but the above is by far the most common.
Where to look? The Java runtime system needs to know where to find programs that you want to run and libraries that are needed. It knows where the predefined Java packages are, but if you are using additional packages, you must tell specify where they are located.
CLASSPATH. For Windows the easiest way is to set the environment variable CLASSPATH, which Java uses to see where it should find Java programs and libraries.
Automatic? Some IDEs tell the Java runtime system where to search, and double-clickable Jar (Java Archive) files don't have this problem
When do you need it? If you compile "by hand"
java in a command window),
or sometimes with TextPad or other editors.
Startbutton in the lower left of the screen.
Control Panelfrom the pop-up menu.
Systemfrom the submenu.
Environment Variablesbutton near the bottom and you will see two lists of variables.
System variableslist for a variable named
CLASSPATH. If you find it, click
Edit. If you don't find it, click
Variable valuefield is a list of file paths of directories or
jarfiles. The first thing in this list should be the current directory, which is represented in windows just as it is in Unix, as a single period. If there's more than one thing in this list, separate items with a semicolon. For example, my CLASSPATH variable starts with these three items (there are a couple more, but this should be enough to give you the idea). The only part you need is the first "dot".
.;C:\classpath\com.fredswartz.ezgui.jar;c:\classpath\TableLayout.jar;I put extra libraries that I want to be searched in a directory named
classpath, but you can choose any name.
CLASSPATHcan be found in Java Glossary : classpath.