What does java classpath mean?

The Java classpath is the path used by the Java Virtual Machine (JVM) to locate class files. It is a collection of multiple directories and JAR files that specify the locations where the JVM searches and loads class files when executing Java programs.

When the JVM runs a Java program, it needs to locate the corresponding class file based on the class’s fully qualified name. The classpath instructs the JVM on where to search for class files in directories or JAR files. If the class file is not found in the specified path of the classpath, the JVM will not be able to locate it and will throw a ClassNotFoundException.

The classpath can be specified in the following ways:

1. You can specify the classpath using command line options. For example, use the “-cp” or “-classpath” option like this: java -cp /path/to/classes:/path/to/lib/mylib.jar MainClass.
2. Utilize system environment variables: You can set the classpath to an environment variable, and the JVM will automatically use the value specified by this environment variable as the classpath. For example, set CLASSPATH to “/path/to/classes:/path/to/lib/*”.
3. Developers often use Java build tools such as Maven and Gradle to automatically set the classpath, which is typically generated based on the project’s configuration files like pom.xml or build.gradle.

It is important to note that the classpath searches for class files in a specific order. The JVM will search through the specified paths in the classpath, in the order they are listed, until it finds the required class file. Therefore, when setting the classpath, make sure that the path containing the class files has a higher priority in the classpath to avoid loading the wrong class files.