1. JVM Structure

2. Class Loader SubSystem

• Loading: finding and importing the binary data for a type
• Linking: performing verification, preparation, and (optionally) resolution
  1. Verification: ensuring the correctness of the imported type
  2. Preparation: allocating memory for class variables and initializing the memory to default values
  3. Resolution: transforming symbolic references from the type into direct references.
• Initialization: invoking Java code that initializes class variables to their proper starting values.

Parent-Delegation Model

• Bootstrap Class Loader: $JAVA_HOME/jre/lib/rt.jar, controlled by -Xbootclasspath option
• Extension Class Loader: %JAVA_HOME/jre/lib/ext/*.jar, controlled by -Djava.ext.dirs system property
• Application/System Class Loader: $CLASSPATH, controlled by -classpath/-cp/$CLASSPATH
• User defined classloader: custom classpath [path on disk, a network address etc]

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