To run Java applications optimally, the JVM divides memory into stack and heap memory. Whenever new variables and objects are declared, new methods are called or other similar operations are performed, the JVM designates memory to these operations from either the Stack Memory or Heap Space. Heap space is used for the dynamic memory allocation of Java objects and classes at runtime. New objects are always created in the heap space, and references to these objects are stored in the stack memory.

Like most modern programming languages, Java includes the concept of exceptions to handle both errors and "exceptional events." When an exception occurs in your code, it disrupts the normal instruction logic and abnormally terminates the process. However, with a little foresight and code, you can often handle these exceptions gracefully, allowing your code to continue running and providing insight for tracking down the root cause of the unexpected result.

Spring Boot has made the Spring Framework more accessible than it already was. It is a streamlined form of the larger Spring Framework. For one, Spring uses manual configurations while Spring Boot contains a number of default config templates. Spring has a number of dependencies; Spring Boot, not so much (at least until build time). Auto-configuration makes it easy to get started with the Spring Framework (or even Java overall if you’re a true novice to coding) and the support community is huge.

The NoClassDefFoundError is a runtime error in Java that occurs if the Java Virtual Machine (JVM) or a ClassLoader instance attempts to load the definition of a class that could not be found. The class definition exists at compile-time but is not available at runtime.

A Java stack trace is displayed when an error or exception occurs. The stack trace, also called a backtrace, consists of a collection of stack records, which store an application's movement during its execution. The stack trace includes information about program subroutines and can be used to debug or troubleshoot and is often used to create log files. These exceptions could be custom (defined by the user) or built-in.

Most programming languages are built on procedural programming, but there is this niche of dialects built for “functional programming,” where code classes are dynamically created based on the rules in the functions you write. If you could put languages on a scale of most procedural to most functional, you’d find Clojure sitting at the edge of the latter. What is Clojure? Who uses Clojure? What’s the best Clojure use case?

null is a reserved word (keyword) in Java for literal values. It is a literal similar to the true and false. In Java, null is a keyword much like the other keywords public, static or final. It is just a value that shows that the object is referring to nothing. The invention of the word “null” originated to denote the absence of something. For example, the absence of the user, a resource, or anything.

The UnknownHostException is an exception in Java that is thrown to indicate that the IP address of a host could not be determined. Since the UnknownHostException is a checked exception, it either needs to be thrown or surrounded by a try-catch block in code.

The SocketException is an exception in Java that is thrown to indicate that an error was encountered while creating or accessing a Socket. Since the SocketException is a checked exception, it either needs to be thrown or surrounded by a try-catch block in code.

One of the most important features of Java is the built-in garbage collector (GC), which automates memory management. The GC is capable of handling the majority of memory leak issues because it implicitly handles memory allocation and freeing. While the GC is capable of handling a significant amount of memory, it does not provide a guaranteed solution to memory leaks. The GC is intelligent, but not without flaws. Even with the most attentive developer's applications, memory leaks can occur.