search
HomeJavajavaTutorialHow does Java JUC operate a collection of List security classes?

Unsafe collection

In single-threaded applications, new ArrayList() is usually used to specify a List collection to store repeatable data.

But under multi-threading, unexpected problems often occur. The code is as follows:

import java.util.*;
public class ListTest {
    public static void main(String[] args) throws InterruptedException {
        // 创建list集合
        //List<string> lists = Arrays.asList("1", "2", "3");
        // 不安全
        List<string> lists = new ArrayList();

        // 开启十个线程增加数据
        for (int i = 1; i {
                lists.add(UUID.randomUUID().toString().substring(0,5));
                System.out.println(Thread.currentThread().getName()+"=="+lists);
            },String.valueOf(i)).start();
        }
    }
}</string></string>

When multiple threads operate the same collection of object information, a java.util.ConcurrentModificationException error often occurs. information.

Security measures provided in Java

In the Java language, a new List collection, the java.util.Vector class, is provided. See the following code for details:

import java.util.*;
public class ListTest {
    public static void main(String[] args) throws InterruptedException {
        // 创建list集合
        //List<string> lists = Arrays.asList("1", "2", "3");
        // 不安全
        //List<string> lists = new ArrayList();
		List<string> lists = new Vector();

        // 开启十个线程增加数据
        for (int i = 1; i {
                lists.add(UUID.randomUUID().toString().substring(0,5));
                System.out.println(Thread.currentThread().getName()+"=="+lists);
            },String.valueOf(i)).start();
        }
    }
}</string></string></string>

There will be no java.util.ConcurrentModificationException error message.

Why can we ensure the safe operation of data?

Java JUC怎么操作List安全类的集合

Adopts synchronized to lock the method execution caller to ensure the multi-thread security of the add operation!

Security List collection under JUC

Under the JUC package, the following ways to create a security collection are provided.

  • Method 1: Collections.synchronizedList(new ArrayList());

import java.util.*;
public class ListTest {
    public static void main(String[] args) throws InterruptedException {
		List<string> lists = Collections.synchronizedList(new ArrayList());

        // 开启十个线程增加数据
        for (int i = 1; i {
                lists.add(UUID.randomUUID().toString().substring(0,5));
                System.out.println(Thread.currentThread().getName()+"=="+lists);
            },String.valueOf(i)).start();
        }
    }
}</string>

View the underlying source code to implement the logic

Java JUC怎么操作List安全类的集合

Determine the incoming list collection type and determine whether the type is java.util.RandomAccess. If so, use java.util.Collections.SynchronizedRandomAccessList to construct the collection. If not, use java.util.Collections.SynchronizedList constructs a collection.

The corresponding add operation logic in the source code is as follows:

Java JUC怎么操作List安全类的集合

Adopt the synchronized synchronization code block method to add data Operation to achieve locking!

  • Method 2: new CopyOnWriteArrayList();

import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
public class ListTest {
    public static void main(String[] args) throws InterruptedException {
        List<string> lists = new CopyOnWriteArrayList();

        // 开启十个线程增加数据
        for (int i = 1; i {
                lists.add(UUID.randomUUID().toString().substring(0,5));
                System.out.println(Thread.currentThread().getName()+"=="+lists);
            },String.valueOf(i)).start();
        }
    }
}</string>

The introduction in the source code is as follows:

Java JUC怎么操作List安全类的集合

Java JUC怎么操作List安全类的集合

Obviously, the logic is as follows:

  1. After calling the add method, get java.util.concurrent.locks .ReentrantLock object information.

  2. Call lock.lock() to get the lock!

  3. Copy the original array object and create a new array with the original array size 1.

  4. Put new data into a new array.

  5. Any operation finally will release the lock!

In terms of performance

The Lock operation under the JUC package has better performance than synchronized!

The above is the detailed content of How does Java JUC operate a collection of List security classes?. For more information, please follow other related articles on the PHP Chinese website!

Statement
This article is reproduced at:亿速云. If there is any infringement, please contact admin@php.cn delete
How does IntelliJ IDEA identify the port number of a Spring Boot project without outputting a log?How does IntelliJ IDEA identify the port number of a Spring Boot project without outputting a log?Apr 19, 2025 pm 11:45 PM

Start Spring using IntelliJIDEAUltimate version...

How to elegantly obtain entity class variable names to build database query conditions?How to elegantly obtain entity class variable names to build database query conditions?Apr 19, 2025 pm 11:42 PM

When using MyBatis-Plus or other ORM frameworks for database operations, it is often necessary to construct query conditions based on the attribute name of the entity class. If you manually every time...

How to use the Redis cache solution to efficiently realize the requirements of product ranking list?How to use the Redis cache solution to efficiently realize the requirements of product ranking list?Apr 19, 2025 pm 11:36 PM

How does the Redis caching solution realize the requirements of product ranking list? During the development process, we often need to deal with the requirements of rankings, such as displaying a...

How to safely convert Java objects to arrays?How to safely convert Java objects to arrays?Apr 19, 2025 pm 11:33 PM

Conversion of Java Objects and Arrays: In-depth discussion of the risks and correct methods of cast type conversion Many Java beginners will encounter the conversion of an object into an array...

How do I convert names to numbers to implement sorting and maintain consistency in groups?How do I convert names to numbers to implement sorting and maintain consistency in groups?Apr 19, 2025 pm 11:30 PM

Solutions to convert names to numbers to implement sorting In many application scenarios, users may need to sort in groups, especially in one...

E-commerce platform SKU and SPU database design: How to take into account both user-defined attributes and attributeless products?E-commerce platform SKU and SPU database design: How to take into account both user-defined attributes and attributeless products?Apr 19, 2025 pm 11:27 PM

Detailed explanation of the design of SKU and SPU tables on e-commerce platforms This article will discuss the database design issues of SKU and SPU in e-commerce platforms, especially how to deal with user-defined sales...

How to set the default run configuration list of SpringBoot projects in Idea for team members to share?How to set the default run configuration list of SpringBoot projects in Idea for team members to share?Apr 19, 2025 pm 11:24 PM

How to set the SpringBoot project default run configuration list in Idea using IntelliJ...

See all articles

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

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.