JVM
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The Java Virtual Machine (JVM) is an abstract computing machine that executes Java bytecode. It has several core components including a class loader, memory areas like the heap and stack, and an execution engine. The execution engine initially interprets bytecode instructions but can optimize performance by just-in-time compiling frequently used bytecode into native machine code. The JVM provides a layer of abstraction between Java applications and the underlying hardware or operating system.
JVM
- 2. 2 What do you mean by JVM? The abstract specification A concrete implementation A runtime instance What is a Java Virtual Machine? JVM Overview
- 6. 6 Class Loader Cont.. Class Loader
- 7. 7 Java Memory Area Memory Management
- 8. 8 Java Memory Area Cont.. Memory Management
- 9. 9 PC Register Each thread of a running program has its own PC register PC register is created when the thread is started As a thread executes a Java method, PC register contains the instruction currently being executed by the thread Memory Management Keeps track of the current instruction executing at any moment
- 10. 10 JVM Stack Stack frame: One stack frame is created whenever a method is executed in the JVM, and the stack frame is added to the JVM stack of the thread Local variable: The parameters sent to the method are saved. After the method parameters, the local variables of the method are saved Memory Management Operand stack: An actual workspace of a method. Each method exchanges data between the Operand stack and the local variable array, and pushes or pops other method invoke results
- 11. 11 Native method stack In other words, it is a stack used to execute C/C++ codes invoked through JNI According to the language, a C stack or C++ stack is created Memory Management Stack for native code written in a language other than Java
- 14. 14 Execution Engine Interpreter: Reads, interprets and executes the bytecode instructions one by one. JVM Execution engine JIT compiler: The execution engine runs as an interpreter first, and at the appropriate time, the JIT compiler compiles the entire byte code to change it to native code
- 15. 15 Execution Engine - JIT Compiler JVM Execution engine JIT compiler: The execution engine runs as an interpreter first, and at the appropriate tie, the JIT compiler compiles the entire byte code to change it to native code
- 16. Questions ???