Home Java javaTutorial Detailed explanation of Java virtual machine

Detailed explanation of Java virtual machine

Mar 18, 2017 pm 05:52 PM


1. The main structure of JVM is as follows:




## 2. Introduction to the functions of each area


1), Method Area:

(1) Used to store virtual Machine-loaded class information,

constants, staticvariables, etc. are memory areas shared by each thread;

(2) The default minimum value is 16MB and the maximum value is 64MB. You can limit the size of the method area through the -XX:PermSize and -XX:MaxPermSize parameters;

(3) There is also a part of the method area that is

Runtime constant pool, mainly used to store literals and symbols generated during compilationReference, constants can also be generated at runtime, such as the intern method of String;

(4) Like the Java heap, it does not require continuous memory and can choose a fixed size or expandable. You can also choose not to implement garbage collection.

2), stack:

(1) The Java virtual machine stack is

thread private, life cycle and The threads are the same.

(2) When each method is executed, a stack frame is created at the same time, which is used to store local variable tables, operation stacks, dynamic links, method exits and other information. The execution process of each method corresponds to the stack frame

entering and exiting the stack.

(3) The local variable table in the JVM virtual machine stack stores various basic

data types that are known at compile time. The space required for the local variable table is allocated at compile time.

(4) Stack frame is the basic data structure during method runtime.

3), Native Method Stack:

(1) The local method stack serves the Native methods used by the JVM virtual machine.

4), Heap:

(1) The largest piece of memory managed by the Java virtual machine.

(2) The Java heap is an area shared by all threads and is created when the virtual machine starts.

(3) The only purpose of the memory area is to store

object instances. All object instances and arrays allocate memory on the heap.

(4) The Java heap is the memory area mainly managed by the JVM garbage collection mechanism. The Java heap can be in a discontinuous memory space in the memory.

5), program counter:

(1) A relatively small memory space, its function can be regarded as the line number indication of the bytecode executed by the current thread Device

(2) When the bytecode interpreter works, it selects the next bytecode instruction, branch, loop, jump, # by changing the value of this counter. ##Exception handling, thread recovery, etc. all need to rely on the program counter.

6), Runtime constant pool:

(1) The runtime constant pool is part of the method area.

(2) In addition to the class version, fields, methods,

Interface description and other information, the Class file also has a constant pool for storage. Various literals and symbol references generated during compilation will be stored in the runtime constant pool in the method area after the class is loaded.

7), direct memory:

Since Java introduced NIO and introduced the IO method of channel and buffer, you can call the Native method to directly allocate off-heap memory. This off-heap memory is local memory and will not affect the heap memory size.

Related articles:

In-depth understanding of Java virtual machine

Java virtual machine learning-class loading mechanism

Java Virtual Machine Learning - Object Memory Allocation and Recycling

Java Virtual Machine Learning - Object Access

The above is the detailed content of Detailed explanation of Java virtual machine. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Java Spring Interview Questions Java Spring Interview Questions Aug 30, 2024 pm 04:29 PM

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

Break or return from Java 8 stream forEach? Break or return from Java 8 stream forEach? Feb 07, 2025 pm 12:09 PM

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

TimeStamp to Date in Java TimeStamp to Date in Java Aug 30, 2024 pm 04:28 PM

Guide to TimeStamp to Date in Java. Here we also discuss the introduction and how to convert timestamp to date in java along with examples.

Java Program to Find the Volume of Capsule Java Program to Find the Volume of Capsule Feb 07, 2025 am 11:37 AM

Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4

PHP: A Key Language for Web Development PHP: A Key Language for Web Development Apr 13, 2025 am 12:08 AM

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

PHP vs. Python: Understanding the Differences PHP vs. Python: Understanding the Differences Apr 11, 2025 am 12:15 AM

PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.

Create the Future: Java Programming for Absolute Beginners Create the Future: Java Programming for Absolute Beginners Oct 13, 2024 pm 01:32 PM

Java is a popular programming language that can be learned by both beginners and experienced developers. This tutorial starts with basic concepts and progresses through advanced topics. After installing the Java Development Kit, you can practice programming by creating a simple "Hello, World!" program. After you understand the code, use the command prompt to compile and run the program, and "Hello, World!" will be output on the console. Learning Java starts your programming journey, and as your mastery deepens, you can create more complex applications.

How to Run Your First Spring Boot Application in Spring Tool Suite? How to Run Your First Spring Boot Application in Spring Tool Suite? Feb 07, 2025 pm 12:11 PM

Spring Boot simplifies the creation of robust, scalable, and production-ready Java applications, revolutionizing Java development. Its "convention over configuration" approach, inherent to the Spring ecosystem, minimizes manual setup, allo

See all articles