The Java ClassLoader is a crucial component of the Java Runtime Environment (JRE) that dynamically loads Java classes into the Java Virtual Machine (JVM) during runtime. This mechanism is essential for Java's runtime class loading capability, which allows classes to be loaded as they are required, rather than loading all classes at startup, thus enhancing performance and flexibility[1][2][3][4][5][6][7][8][9][10][11][12].
Key Functions of the Java ClassLoader
Dynamic Class Loading: The ClassLoader loads classes dynamically, meaning it loads classes at the time they are needed during execution, not all at once at startup. This is particularly useful in large applications that use a significant number of classes, potentially reducing the initial loading time and memory footprint[1][3][5][6].
Delegation Model: Java ClassLoaders use a delegation hierarchy model to load classes. When a ClassLoader is asked to load a class, it delegates the task to its parent class loader. If the parent cannot find the class, the ClassLoader itself attempts to load the class. This model helps to maintain a clean organization where the system classes do not interfere with user-defined classes[1][2][3][4][5][6][7][8][9].
Types of ClassLoaders:
Bootstrap ClassLoader: This is the root of the class loader hierarchy and is part of the core JVM. It loads the fundamental Java classes like java.lang.Object and other classes from the Java Standard Library located in the rt.jar file[1][2][3][4][5][6].
Extension ClassLoader: This loads classes that are part of the extensions directory (jre/lib/ext, or any other directory specified by the java.ext.dirs system property)[1][2][3][4][5][6].
System/Application ClassLoader: It loads classes found in the classpath environment variable, -classpath or -cp command line option. It is typically used to load ...
