Memory management: The JVM manages memory automatically vis its built-in garbage collector, which frees up memory when the program is finished with it, saving the developer from having to account for memory allocation and deallocation.Platform independence: The JVM includes a platform-independent runtime environment which allows for the execution of Java applications on most hardware and software architectures.The Java Virtual Machine has several key features that make it such a powerful and invaluable platform including platform independence, memory management, security, dynamic loading, JIT compilation, and multithreading: Read: Java Best Practices What are the Features of the JVM? Garbage collection frees up memory resources that are no longer being used by the program or CPU, allowing the memory to be reclaimed by the JVM and put to other uses. Garbage CollectionĪs the application is executing, the Java Virtual Machine manages memory resources (allocating and deallocating) by performing automatic garbage collection. We discuss JIT in more detail in a section below. During JIT compilation, the JVM compiles frequently executed bytecode into native machine language, which is executed with more efficiency than interpreted bytecode. Once the code has been interpreted, the JVM may uses Just-In-Time (JIT) compilation to improve performance. While each instruction is executed, the JVM maintains a stack of values to be used by any following sets of instructions. Next, the JVM has to interpret the bytecode and sequentially execute each instruction. This preparation includes memory allocation for any required objects and initializing static variables. Once the bytecode is verified, the Java Virtual Machine preps the memory and resources needed in order for the program to execute. VerificationĪfter bytecode is loaded into memory, the JVM needs to verify its correctness, which it does by checking the Java bytecode for violations of the Java language specification, including illegal access to private fields or private methods. This task is performed by the class loader, whose responsibility is to locate any necessary bytecode files and load them into system memory. The very first step that occurs in the JVM process involves loading the Java bytecode into the JVM. To answer the question, “How does the JVM work?” developers must first understand the steps the JVM follows in order to interpret Java code and then execute it. At runtime, the JVM interprets the resultant bytecode and translates it into native machine code, accounting for the characteristics of the underlying system it will run on. ![]() This concept of WORA is achieved courtesy of a layer of abstraction residing between the Java code and the underlying OS and hardware. Java’s JVM is platform-independent, meaning Java programs can be written once and run on any JVM implementation – a principle known as WORA or write once, run anywhere. When applications written in Java are compiled, they produce bytecode, which can be executed (or run) by any JVM implementation, regardless of the underlying architecture, hardware, or operating system. Its role is simple: interpret and execute Java bytecode, which a low-level representation of the compiled form of a piece of Java code. The Java Virtual Machine is a virtual “machine” that provides a runtime environment for Java applications and programs. Read: Java Tools to Increase Productivity What is the JVM? In this programming tutorial, we discuss what the JVM is, how it works, and its key features for developers. The Java Virtual Machine, or JVM, is a key component of the Java programming language, providing a platform-independent environment for the execution of Java code across most major hardware, operating systems, and software architectures.
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