The classpath tells applications where to find third-party and user-defined classes. It defines the search order for classes and resources, including Java platform classes, extension classes, and user classpath entries. The classpath can be set using the -classpath option with Java tools or using the CLASSPATH environment variable, with -classpath being preferred. Classpath entries can refer to directories, JAR files, or ZIP files containing classes. Multiple path entries are separated by semicolons.

1. Classpath
• Tells applications where to find third-party and user-
defined classes
• The search order used by java tools
• Java platform (bootstrap) classes, any extension classes, and
the class path
• Two ways to change class path
• -classpath option change the class path of java tools
• CLASSPATH environment variable
• The first approach is preferred
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2. Setting the Classpath
• -classpath
• jdkTool -classpath path1;path2...
– eg. : javac –classpath d:projectclasses
• CLASSPATH environment variable
• eg. : SET CLASSPATH d:projectclasses
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3. Classpath and Archive files
• Classes can be stored either in directories (folders) or in
archive files ( jar files)
• eg. The Java platform classes are stored in rt.jar.
• Class path to the archive files
• For a .jar or .zip file that contains .class files, the path ends with
the name of the .zip or .jar file
• eg. : javac –classpath d:projectutilClasses.zip
• eg. : javac –classpath e:xmlxalan.jar
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4. Multiple Path Entries
• Multiple path entries are separated by semi-colons
• To find class files in the following directories
• C:javaMyClasses
• C:javaOtherClasses
• set the classpath to:
• C:> java –classpath C:javaMyClasses;C:javaOtherClasses
• Order of classpath entries is important
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