The class loading component is fundamental to the Java virtual machine. Though developers generally have a good grasp of the basics of class loading, when a problem occurs, they may have a hard time diagnosing and determining a solution. In this four-part article series, we discuss the various class loading problems that you may encounter in your Java development and illustrate why they occur and how to resolve them. These insights should help you understand and resolve common Java exceptions, such as NoClassDefFoundError and ClassNotFoundException, in addition to more challenging problems, such as class loader constraint violations and deadlocks. In this first article, we describe in detail how Java class loading works and discuss the tools available in the JVM to help you diagnose class loading problems.