Home Java javaTutorial An in-depth exploration of the inner workings of the JVM: a detailed analysis from memory processing to garbage collection

An in-depth exploration of the inner workings of the JVM: a detailed analysis from memory processing to garbage collection

Feb 18, 2024 pm 10:41 PM
Garbage collector String constant

An in-depth exploration of the inner workings of the JVM: a detailed analysis from memory processing to garbage collection

Understand the principles of JVM: a comprehensive analysis from memory management to garbage collection

With the widespread application of the Java language, the Java Virtual Machine (JVM) has become the core of Java program execution important environment. Understanding JVM principles is very important for Java developers, which can help programmers optimize code and adjust performance. This article will comprehensively analyze the JVM's memory management and garbage collection mechanism, and provide specific code examples to help readers better understand.

  1. JVM Overview
    JVM is one of the core components of Java program execution. It is responsible for translating Java bytecode (.class file) into machine code and executing it. The JVM is independent of hardware and operating systems, which makes Java programs cross-platform.
  2. JVM memory structure
    The memory structure of JVM mainly includes the following parts:
  3. Method Area: used to store metadata information of classes, such as classes, methods, field information.
  4. Heap: used to store object instances.
  5. Stack (Stack): used to store local variables, operand stacks and other data for method calls.
  6. Program Counter: used to record the address of the bytecode instruction executed by the current thread.
  7. Native Method Stack: used to store data related to local method calls.

The following is a simple code example that demonstrates the memory structure of the JVM:

public class MemoryStructureExample {
    // 静态方法区
    static String staticVar = "Static variable";
  
    public static void main(String[] args) {
        // 程序计数器
        int pc = 0;
      
        // 栈
        int localVar = 10;
        int result = add(5, 3);
        System.out.println("Result: " + result);
      
        // 堆
        Object obj = new Object();
        System.out.println(obj.toString());
    }
  
    // 方法区
    public static int add(int a, int b) {
        return a + b;
    }
}
Copy after login
  1. JVM Memory Management
    The JVM automatically manages memory through the garbage collection mechanism, providing With the function of automatic memory allocation and release, developers do not need to manually manage memory. The memory management of JVM mainly includes the following aspects:
  • Heap memory management: Object instances dynamically created in Java programs are stored in the heap. The JVM automatically recycles no longer used objects through the garbage collector to free up memory space. The initial size and maximum size of the Java heap can be set through the -Xms and -Xmx parameters.
  • Stack memory management: The stack is used to store data such as local variables and operand stacks for method calls. Each thread creates a stack frame when executing a method to store method-related data. When the method is executed, the corresponding stack frame will be destroyed. The size of the stack can be set through the -Xss parameter.
  • Method area and runtime constant pool management: The method area in the JVM is used to store metadata information of the class. The runtime constant pool is part of the method area and is used to store string constants and symbol references. The JVM uses the garbage collector to garbage collect the method area and release class information and constants that are no longer used.
  1. Garbage collection algorithm
    There are two main types of JVM garbage collection algorithms: mark-clear algorithm and copy algorithm.
  • Mark-clear algorithm: This algorithm marks objects that are no longer used and then clears them. But this algorithm has an obvious shortcoming, which will generate a lot of memory fragmentation.
  • Copy algorithm: This algorithm divides the memory into two areas, namely Eden space and Survivor space. The object is first allocated to the Eden space. When the Eden space is insufficient, the Minor GC is triggered and the surviving objects are copied to the Survivor space. After multiple collections, surviving objects will be copied to the old generation. This algorithm reduces memory fragmentation, but wastes some memory space.
  1. Garbage Collector
    JVM provides a variety of garbage collectors for performing garbage collection operations. Common garbage collectors include serial collectors, parallel collectors and CMS collectors.
  • Serial Collector: The serial collector is the simplest garbage collector, using a single thread for garbage collection. Suitable for low-load application scenarios in single-core processors or multi-core processors.
  • Parallel Collector: The parallel collector uses multiple threads for garbage collection and can take full advantage of multi-core processors. Suitable for high-load application scenarios in multi-core processors.
  • CMS collector (Concurrent Mark and Sweep Collector): The CMS collector is a low-pause garbage collector that performs garbage collection through two stages: concurrent marking and concurrent clearing. Suitable for application scenarios with high pause time requirements.

The following is a code example that demonstrates the garbage collection mechanism of the JVM:

public class GarbageCollectionExample {
    public static void main(String[] args) {
        for (int i = 0; i < 1000000; i++) {
            Object obj = new Object();
            System.gc();
        }
    }
}
Copy after login

With the above code example, objects can be created in a loop and called after each object creation System.gc() method triggers garbage collection operation.

Summary:
This article comprehensively analyzes the memory management and garbage collection mechanism of JVM. By understanding the JVM's memory structure, memory management and garbage collection algorithms, as well as common garbage collectors, developers can help developers better optimize code and adjust performance to improve application execution efficiency. The memory structure and garbage collection mechanism of JVM are demonstrated through specific code examples. I hope it will be helpful for readers to understand the principles of JVM.

The above is the detailed content of An in-depth exploration of the inner workings of the JVM: a detailed analysis from memory processing to garbage collection. 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

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

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)

What are string constants in sql What are string constants in sql May 08, 2024 am 09:54 AM

String constants in SQL are special values ​​used to represent text data, enclosed in single quotes (') or double quotes ("), and can contain any characters. They are of two types: single quoted string constants and double quotes String constants are widely used in condition specification, data provision, derived column creation and function parameters. Single quotes are usually used, but double quotes can contain single quote characters and span multiple lines.

Why does golang compile quickly? Why does golang compile quickly? Apr 21, 2024 am 01:25 AM

Go has the advantage of fast compilation due to factors such as parallel compilation, incremental compilation, simple syntax, efficient data structures, precompiled headers, garbage collection, and other optimizations.

The role and potential of Golang in desktop application development The role and potential of Golang in desktop application development Apr 08, 2024 pm 03:33 PM

Role of Go in Desktop Application Development: Go is an ideal choice for desktop application development due to its cross-platform nature, concurrency, simplicity and garbage collection mechanism. Potential: Cross-platform tools: Create tools that run on multiple platforms. Efficient applications: Take advantage of concurrency to process data and improve performance. GUI Apps: Easily create modern GUI interfaces. Game Development: Develop low-latency, high-performance games.

Go language helps efficient operation and maintenance: a practical guide Go language helps efficient operation and maintenance: a practical guide Apr 08, 2024 pm 03:51 PM

Go language is widely used in the field of operation and maintenance. This article provides a practical guide showing how to use Go language to solve common operation and maintenance tasks, such as indicator collection and monitoring. Other operational use cases include log aggregation, automated configuration management and troubleshooting. The high concurrency and ease of use of the Go language make it an ideal choice for operation and maintenance engineers. Through the practical cases and use cases introduced in this article, the operation and maintenance team can improve efficiency and simplify key tasks.

How does Java anonymous inner class solve memory leak problem? How does Java anonymous inner class solve memory leak problem? May 01, 2024 pm 10:30 PM

Anonymous inner classes can cause memory leaks. The problem is that they hold a reference to the outer class, preventing the outer class from being garbage collected. Solutions include: 1. Use weak references. When the external class is no longer held by a strong reference, the garbage collector will immediately recycle the weak reference object; 2. Use soft references. The garbage collector will recycle the weak reference object when it needs memory during garbage collection. Only then the soft reference object is recycled. In actual combat, such as in Android applications, the memory leak problem caused by anonymous inner classes can be solved by using weak references, so that the anonymous inner class can be recycled when the listener is not needed.

Golang applicability: comprehensive analysis of its advantages and disadvantages Golang applicability: comprehensive analysis of its advantages and disadvantages Apr 08, 2024 pm 05:09 PM

Golang is suitable for concurrent processing and high-performance scenarios, and is popular for its goroutines, high-performance compilation, and concise syntax. Disadvantages include concurrent garbage collection, generic limitations, and ecosystem maturity. Advantages: High concurrency (goroutine) High performance (static compilation) Simple syntax library Rich disadvantages: Garbage collection generics limit ecosystem maturity

Usage of single quotes and double quotes in c language Usage of single quotes and double quotes in c language May 02, 2024 pm 02:36 PM

Summary: Single quotes and double quotes in C language are used to define string constants. Single quotes define a character array with a limited length, which is stored in the data area and can be modified; double quotes define a string constant that is stored in the code area and has a limited length. Restricted, cannot be modified, may contain escape characters.

Memory leaks in PHP applications: causes, detection and resolution Memory leaks in PHP applications: causes, detection and resolution May 09, 2024 pm 03:57 PM

A PHP memory leak occurs when an application allocates memory and fails to release it, resulting in a reduction in the server's available memory and performance degradation. Causes include circular references, global variables, static variables, and expansion. Detection methods include Xdebug, Valgrind and PHPUnitMockObjects. The resolution steps are: identify the source of the leak, fix the leak, test and monitor. Practical examples illustrate memory leaks caused by circular references, and specific methods to solve the problem by breaking circular references through destructors.

See all articles