In Java, annotations are metadata that you can attach to code elements (classes, methods, variables, parameters, packages, etc.) to give additional information to the compiler, tools, or runtime.They do not directly affect the execution of code but can influence it through processing (for example, frameworks like Spring or JUnit use annotations heavily). 1. Basic…
ThreadLocal in Java is a special class that provides thread-local variables. Each thread that accesses a ThreadLocal variable has its own, independently initialized copy of the variable. This is extremely useful when you want to avoid sharing data between threads, such as in cases of per-thread counters, user sessions, or database connections. Here’s a…
In Java, throw, throws, and finally are related to exception handling, but they have very different purposes. 1. throw Purpose: Used inside a method to actually throw an exception object. Syntax: throw new ExceptionType("message"); Key Points: Works with a single exception instance at a time. Control jumps immediately to the nearest matching catch block…
In Java, try, catch, and throws are part of the exception handling system. They let you deal with errors without crashing your program. Here’s the breakdown: 1. try A block of code where you write code that might throw an exception. If an exception happens inside try, Java will look for a matching catch…
In Java, exceptions are broadly divided into three main categories, based on how the compiler and runtime handle them: 1. Checked Exceptions Definition: Exceptions that are checked at compile-time. If your code might throw a checked exception, you must either handle it with a try-catch block or declare it with throws. These are typically…
1. Nested Classes in Java A nested class is any class defined inside another class. Java allows classes to be nested for better organization, encapsulation, and readability. There are two main types: A. Static Nested Class Declared static inside another class. Can access only static members of the outer class directly. Does not have…
Java’s history is a mix of big ideas, clever engineering, and a little bit of luck. Here’s the story in a clear timeline form: 1. Origins (1991–1994) – The Green Project In 1991, a small team at Sun Microsystems led by James Gosling, Patrick Naughton, and Mike Sheridan started the Green Project. The original…
YearVersionKey Features1996JDK 1.0First official release; basic core libraries, applets.1997JDK 1.1Inner classes, JDBC, JavaBeans, RMI.1998J2SE 1.2Swing GUI, Collections Framework, JIT compiler.2000J2SE 1.3HotSpot JVM, Java Naming and Directory Interface (JNDI).2002J2SE 1.4assert keyword, NIO (New I/O), logging API, XML parsing.2004J2SE 5.0Generics, annotations, enhanced for loop, autoboxing, varargs.2006Java SE 6Scripting API, improvements in web services, compiler API.2011Java SE…
1. JVM (Java Virtual Machine) Definition: JVM is the engine that runs Java bytecode. Role: It converts compiled Java bytecode into machine code so your program can run on any device. Key Point: JVM is platform-dependent (different JVMs exist for Windows, Linux, Mac). Example: You write code once, compile it, and JVM allows it…
In Java, access specifiers (also called access modifiers) define the visibility and accessibility of classes, methods, variables, and constructors. They control which parts of a program can access certain members of a class. Java has four main access specifiers: 1. public Visibility: Everywhere, i.e., from any other class or package. Usage: When you want…