The purpose of the classpath is to tell a JVM where to find classes and other resources. The meaning of the classpath and the search process are intertwined.
The classpath is a form of search path which specifies a sequence of locations to look for resources. In a standard classpath, these places are either, a directory in the host file system, a JAR file or a ZIP file. In each cases, the location is the root of a namespace that will be searched.
The standard procedure for searching for a class on the classpath is as follows:
Map the class name to a relative classfile pathname
RP. The mapping for class names to class filenames is described elsewhere.
For each entry
E in the classpath:
Eto give an absolute pathname
APis a path for an existing file.
RPin the JAR / ZIP file index.
The procedure for searching for a resource on the classpath depends on whether the resource path is absolute or relative. For an absolute resource path, the procedure is as above. For a relative resource path resolved using
Class.getResourceAsStream, the path for the classes package is prepended prior to searching.
(Note these are the procedures implemented by the standard Java classloaders. A custom classloader might perform the search differently.)