How 'java' handles classname passed to it

Question

Hi,
After compiling the .java file, the .class is passed to 'java'
and that runs the program.
Does the 'java' work this way: when we give "java classname", 'java'
strictly would search for classname.class and proceeds thereafter,
The reason i got this doubt is when i gave a command "java
classname.class" an error was raised pointing no class definition.
Thanks for your time.
Kris.

Answer 1

When the java virtual machine looks for a class it uses a ClassLoader. What the default classloader does is:
1) Converts any dots in the "fully qualified name" to the appropriate path separater / or \ depending on the operating system.
2) If it's an inner class, the inner class name is separated from the outer class by a $
4) adds .class to the end
5) Walks along the CLASSPATH. For every directory on the CLASSPATH it adds the string processed above and looks for a file. For every .jar file it tries to find the entry of the same string.
Note "." in a classname is used to separated package name from class, as in java.util.Map, for example. "classname.class" would look for a class called "class" in a package called "classname".
You can't compile a class called "class", by the way, because it's a reserved word.